Ammonia mediated carbon dioxide (co2) sequestration methods and systems

ABSTRACT

Methods of sequestering carbon dioxide (CO 2 ) are provided. Aspects of the methods include contacting an aqueous capture ammonia with a gaseous source of CO 2  under conditions sufficient to produce an aqueous ammonium carbonate. The aqueous ammonium carbonate is then combined with a cation source under conditions sufficient to produce a solid CO 2  sequestering carbonate and an aqueous ammonium salt. The aqueous capture ammonia is then regenerated from the from the aqueous ammonium salt. Also provided are systems configured for carrying out the methods.

CROSS-REFERENCE TO RELATED APPLICATIONS

Pursuant to 35 U.S.C. §119(e), this application claims priority to thefiling dates of U.S. Provisional Application Ser. No. 62/313,613 filedon Mar. 25, 2016 and U.S. Provisional Application Ser. No. 62/451,506filed on Jan. 27, 2017; the disclosures of which applications are hereinincorporated by reference.

INTRODUCTION

Carbon dioxide (CO₂) is a naturally occurring chemical compound that ispresent in Earth's atmosphere as a gas. Sources of atmospheric CO₂ arevaried, and include humans and other living organisms that produce CO₂in the process of respiration, as well as other naturally occurringsources, such as volcanoes, hot springs, and geysers.

Additional major sources of atmospheric CO₂ include industrial plants.Many types of industrial plants (including cement plants, refineries,steel mills and power plants) combust various carbon-based fuels, suchas fossil fuels and syngases. Fossil fuels that are employed includecoal, natural gas, oil, petroleum coke and biofuels. Fuels are alsoderived from tar sands, oil shale, coal liquids, and coal gasificationand biofuels that are made via syngas.

The environmental effects of CO₂ are of significant interest. CO₂ iscommonly viewed as a greenhouse gas. Because human activities since theindustrial revolution have rapidly increased concentrations ofatmospheric CO₂, anthropogenic CO₂ has been implicated in global warmingand climate change, as well as increasing oceanic bicarbonateconcentration. Ocean uptake of fossil fuel CO₂ is now proceeding atabout 1 million metric tons of CO₂ per hour.

Concerns over anthropogenic climate change and ocean acidification, havefueled an urgency to discover scalable, cost effective, methods ofcarbon capture and sequestration (CCS). Typically, methods of CCSseparate pure CO₂ from complex flue streams, compress the purified CO₂,and finally inject it into underground saline reservoirs for geologicsequestration. These multiple steps are very energy and capitalintensive.

SUMMARY

Methods of sequestering carbon dioxide (CO₂) are provided. Aspects ofthe methods include contacting an aqueous capture ammonia with a gaseoussource of CO₂ under conditions sufficient to produce an aqueous ammoniumcarbonate. The aqueous ammonium carbonate is then combined with a cationsource under conditions sufficient to produce a solid CO₂ sequesteringcarbonate and an aqueous ammonium salt. The aqueous capture ammonia isthen regenerated from the from the aqueous ammonium salt. Also providedare systems configured for carrying out the methods.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 provides a schematic representation of a system according to anembodiment of the invention.

FIG. 2 provides a schematic representation of a system according to anembodiment of the invention, where ammonia regeneration occurs asub-atmospheric pressure and all heat is provided by waste heat sources.

FIG. 3 provides a plot Carbon dioxide absorption (%) as it depends ongas volume (standard liters per minute, SLPM) using a 0.5 M NH₃solution, with CO₂ gas concentrations ranging from 5-50% CO₂ (air makeupgas) and a single pass through one hollow fiber membrane contactor (1.4m² surface area), as reported in the Experimental Section, below.

FIGS. 4 to 9 provide graphical results of an ammonia reformation studyas reported in the Experimental Section, below.

FIG. 10 provides an illustration of a system according to an embodimentof the invention that is suitable for use with a 2 MW coal fired powerplant.

FIGS. 11A to 11C provide illustrations of systems according to variousembodiments of the invention that is suitable for use with a 2 MW coalfired power plant.

FIG. 12 provides an illustration of a system according to an embodimentof the invention that is suitable for use with a 10 MW coal fired powerplant.

FIG. 13 provides an illustration of a system according to an embodimentof the invention that is suitable for use with a 10 MW coal fired powerplant where the ammonia regenerator is operated at reducedpressure/temperature using waste heat.

DETAILED DESCRIPTION

Methods of sequestering carbon dioxide (CO₂) are provided. Aspects ofthe methods include contacting an aqueous capture ammonia with a gaseoussource of CO₂ under conditions sufficient to produce an aqueous ammoniumcarbonate. The aqueous ammonium carbonate is then combined with a cationsource under conditions sufficient to produce a solid CO₂ sequesteringcarbonate and an aqueous ammonium salt. The aqueous capture ammonia isthen regenerated from the from the aqueous ammonium salt. Also providedare systems configured for carrying out the methods.

Before the present invention is described in greater detail, it is to beunderstood that this invention is not limited to particular embodimentsdescribed, as such may, of course, vary. It is also to be understoodthat the terminology used herein is for the purpose of describingparticular embodiments only, and is not intended to be limiting, sincethe scope of the present invention will be limited only by the appendedclaims.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimit of that range and any other stated or intervening value in thatstated range, is encompassed within the invention. The upper and lowerlimits of these smaller ranges may independently be included in thesmaller ranges and are also encompassed within the invention, subject toany specifically excluded limit in the stated range. Where the statedrange includes one or both of the limits, ranges excluding either orboth of those included limits are also included in the invention.

Certain ranges are presented herein with numerical values being precededby the term “about.” The term “about” is used herein to provide literalsupport for the exact number that it precedes, as well as a number thatis near to or approximately the number that the term precedes. Indetermining whether a number is near to or approximately a specificallyrecited number, the near or approximating un-recited number may be anumber which, in the context in which it is presented, provides thesubstantial equivalent of the specifically recited number.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although any methods andmaterials similar or equivalent to those described herein can also beused in the practice or testing of the present invention, representativeillustrative methods and materials are now described.

All publications and patents cited in this specification are hereinincorporated by reference as if each individual publication or patentwere specifically and individually indicated to be incorporated byreference and are incorporated herein by reference to disclose anddescribe the methods and/or materials in connection with which thepublications are cited. The citation of any publication is for itsdisclosure prior to the filing date and should not be construed as anadmission that the present invention is not entitled to antedate suchpublication by virtue of prior invention. Further, the dates ofpublication provided may be different from the actual publication dateswhich may need to be independently confirmed.

It is noted that, as used herein and in the appended claims, thesingular forms “a”, “an”, and “the” include plural referents unless thecontext clearly dictates otherwise. It is further noted that the claimsmay be drafted to exclude any optional element. As such, this statementis intended to serve as antecedent basis for use of such exclusiveterminology as “solely,” “only” and the like in connection with therecitation of claim elements, or use of a “negative” limitation.

As will be apparent to those of skill in the art upon reading thisdisclosure, each of the individual embodiments described and illustratedherein has discrete components and features which may be readilyseparated from or combined with the features of any of the other severalembodiments without departing from the scope or spirit of the presentinvention. Any recited method can be carried out in the order of eventsrecited or in any other order which is logically possible.

Methods

As summarized above, aspects of the invention include methods ofsequestering CO₂ from a gaseous source of CO₂. Accordingly, aspects ofthe invention include CO₂ sequestration processes, i.e., processes(methods, protocols, etc.) that result in CO₂ sequestration. By “CO₂sequestration” is meant the removal or segregation of an amount of CO₂from an environment, such as the Earth's atmosphere or a gaseous wastestream produced by an industrial plant, so that some or all of the CO₂is no longer present in the environment from which it has been removed.CO₂ sequestering methods of the invention sequester CO₂ by producing asubstantially pure subsurface injectable CO₂ product gas and a solidstorage stable CO₂ sequestering product from an amount of CO₂, such thatthe CO₂ is sequestered. The solid storage stable CO₂ sequesteringproduct is a storage stable composition that incorporates an amount ofCO₂ into a storage stable form, such as an above-ground storage orunderwater storage stable form, so that the CO₂ is no longer present as,or available to be, a gas in the atmosphere. Sequestering of CO₂according to methods of the invention results in prevention of CO₂ gasfrom entering the atmosphere and allows for long-term storage of CO₂ ina manner such that CO₂ does not become part of the atmosphere.

As summarized above, aspects of the methods include: a) contacting anaqueous capture ammonia with a gaseous source of CO₂ under conditionssufficient to produce an aqueous ammonium carbonate; b) combining acation source and the aqueous ammonium carbonate under conditionssufficient to produce a solid CO₂ sequestering carbonate and an aqueousammonium salt; and c) regenerating aqueous capture ammonia from theaqueous ammonium salt, e.g., for subsequent use in further ammoniamediated CO₂ sequestration. Each of these aspects of the methods is nowfurther described in greater detail.

CO₂ Capture

Embodiments of the methods include contacting an aqueous capture ammoniawith a gaseous source of CO₂ (i.e., a CO₂ containing gas) underconditions sufficient to produce an aqueous ammonium carbonate. The CO₂containing gas may be pure CO₂ or be combined with one or more othergasses and/or particulate components, depending upon the source, e.g.,it may be a multi-component gas (i.e., a multi-component gaseousstream). In certain embodiments, the CO₂ containing gas is obtained froman industrial plant, e.g., where the CO₂ containing gas is a waste feedfrom an industrial plant. Industrial plants from which the CO₂containing gas may be obtained, e.g., as a waste feed from theindustrial plant, may vary. Industrial plants of interest include, butare not limited to, power plants and industrial product manufacturingplants, such as, but not limited to, chemical and mechanical processingplants, refineries, cement plants, steel plants, etc., as well as otherindustrial plants that produce CO₂ as a byproduct of fuel combustion orother processing step (such as calcination by a cement plant). Wastefeeds of interest include gaseous streams that are produced by anindustrial plant, for example as a secondary or incidental product, of aprocess carried out by the industrial plant.

Of interest in certain embodiments are waste streams produced byindustrial plants that combust fossil fuels, e.g., coal, oil, naturalgas, as well as man-made fuel products of naturally occurring organicfuel deposits, such as but not limited to tar sands, heavy oil, oilshale, etc. In certain embodiments, power plants are pulverized coalpower plants, supercritical coal power plants, mass burn coal powerplants, fluidized bed coal power plants, gas or oil-fired boiler andsteam turbine power plants, gas or oil-fired boiler simple cycle gasturbine power plants, and gas or oil-fired boiler combined cycle gasturbine power plants. Of interest in certain embodiments are wastestreams produced by power plants that combust syngas, i.e., gas that isproduced by the gasification of organic matter, e.g., coal, biomass,etc., where in certain embodiments such plants are integratedgasification combined cycle (IGCC) plants. Of interest in certainembodiments are waste streams produced by Heat Recovery Steam Generator(HRSG) plants. Waste streams of interest also include waste streamsproduced by cement plants. Cement plants whose waste streams may beemployed in methods of the invention include both wet process and dryprocess plants, which plants may employ shaft kilns or rotary kilns, andmay include pre-calciners. Each of these types of industrial plants mayburn a single fuel, or may burn two or more fuels sequentially orsimultaneously. A waste stream of interest is industrial plant exhaustgas, e.g., a flue gas. By “flue gas” is meant a gas that is obtainedfrom the products of combustion from burning a fossil or biomass fuelthat are then directed to the smokestack, also known as the flue of anindustrial plant.

Waste streams produced by cement plants are also suitable for systemsand methods of the invention. Cement plant waste streams include wastestreams from both wet process and dry process plants, which plants mayemploy shaft kilns or rotary kilns, and may include pre-calciners. Theseindustrial plants may each burn a single fuel, or may burn two or morefuels sequentially or simultaneously. Other industrial plants such assmelters and refineries are also useful sources of waste streams thatinclude carbon dioxide.

Industrial waste gas streams may contain carbon dioxide as the primarynon-air derived component, or may, especially in the case of coal-firedpower plants, contain additional components (which may be collectivelyreferred to as non-CO₂ pollutants) such as nitrogen oxides (NOx), sulfuroxides (SOx), and one or more additional gases. Additional gases andother components may include CO, mercury and other heavy metals, anddust particles (e.g., from calcining and combustion processes).Additional non-CO₂ pollutant components in the gas stream may alsoinclude halides such as hydrogen chloride and hydrogen fluoride;particulate matter such as fly ash, dusts, and metals including arsenic,beryllium, boron, cadmium, chromium, chromium VI, cobalt, lead,manganese, mercury, molybdenum, selenium, strontium, thallium, andvanadium; and organics such as hydrocarbons, dioxins, and PAH compounds.Suitable gaseous waste streams that may be treated have, in someembodiments, CO₂ present in amounts of 200 ppm to 1,000,000 ppm; or 200ppm to 500,000 ppm; or 200 ppm to 100,000 ppm; or 200 ppm to 10,000; or200 ppm to 5,000 ppm; or 200 ppm to 2000 ppm; or 200 ppm to 1000 ppm; or200 to 500 ppm; or 500 ppm to 1,000,000 ppm; or 500 ppm to 500,000 ppm;or 500 ppm to 100,000 ppm; or 500 ppm to 10,000; or 500 ppm to 5,000ppm; or 500 ppm to 2000 ppm; or 500 ppm to 1000 ppm; or 1000 ppm to1,000,000 ppm; or 1000 ppm to 500,000 ppm; or 1000 ppm to 100,000 ppm;or 1000 ppm to 10,000; or 1000 ppm to 5,000 ppm; or 1000 ppm to 2000ppm; or 2000 ppm to 1,000,000 ppm; or 2000 ppm to 500,000 ppm; or 2000ppm to 100,000 ppm; or 2000 ppm to 10,000; or 2000 ppm to 5,000 ppm; or2000 ppm to 3000 ppm; or 5000 ppm to 1,000,000 ppm; or 5000 ppm to500,000 ppm; or 5000 ppm to 100,000 ppm; or 5000 ppm to 10,000; or10,000 ppm to 1,000,000 ppm; or 10.00 ppm to 500,000 ppm; or 10,000 ppmto 100,000 ppm; or 50,000 ppm to 1,000,000 ppm; or 50,000 ppm to 500,000ppm; or 50,000 ppm to 100,000 ppm; or 100,000 ppm to 1,000,000 ppm; or100,000 ppm to 500,000 ppm; or 200,000 ppm to 1000 ppm, including200,000 ppm to 2000 ppm, for example 180,000 ppm to 2000 ppm, or 180,000ppm to 5000 ppm, also including 180,000 ppm to 10,000 ppm.

The waste streams, particularly various waste streams of combustion gas,may include one or more additional non-CO₂ components, for example only,water, NOx (mononitrogen oxides: NO and NO₂), SOx (monosulfur oxides:SO, SO₂ and SO₃), VOC (volatile organic compounds), heavy metals suchas, but not limited to, mercury, and particulate matter (particles ofsolid or liquid suspended in a gas). Flue gas temperature may also vary.In some embodiments, the temperature of the flue gas comprising CO₂ isfrom 0° C. to 2000° C., or 0° C. to 1000° C., or 0.degree ° C. to 500°C., or 0° C. to 100° C., or 0° C. to 50° C., or 10° C. to 2000° C., or10° C. to 1000° C., or 10° C. to 500° C., or 10° C. to 100° C., or 10°C. to 50° C., or 50° C. to 2000° C., or 50° C. to 1000° C., or 50° C. to500° C., or 50° C. to 100° C., or 100° C. to 2000° C., or 100° C. to1000° C., or 100° C. to 500° C., or 500° C. to 2000° C., or 500° C. to1000° C., or 500° C. to 800° C., or such as from 60° C. to 700° C., andincluding 100° C. to 400° C.

As summarized above, an aqueous capture ammonia is contacted with thegaseous source of CO₂ under conditions sufficient to produce an aqueousammonium carbonate. The concentration of ammonia in the aqueous captureammonia may vary, where in some instances the aqueous capture ammoniaincludes ammonia (NH₃) at a concentration ranging from 0.1 to 20.0 M,and in some instances 0.1 to 5.0 M, such as 0.1 to 4.0 M, e.g., 4.0 M,while in other instances from 2 to 20, such as 4 to 20 M. The aqueouscapture ammonia may include any convenient water. Waters of interestfrom which the aqueous capture ammonia may be produced include, but arenot limited to, freshwaters, seawaters, brine waters, produced watersand waste waters. The pH of the aqueous capture ammonia may vary,ranging in some instances from 10.0 to 13.5, such as 10.0 to 13.0,including 10.5 to 12.5.

The CO₂ containing gas, e.g., as described above, may be contacted withthe aqueous capture ammonia using any convenient protocol. For example,contact protocols of interest include, but are not limited to: directcontacting protocols, e.g., bubbling the gas through a volume of theaqueous medium, concurrent contacting protocols, i.e., contact betweenunidirectionally flowing gaseous and liquid phase streams,countercurrent protocols, i.e., contact between oppositely flowinggaseous and liquid phase streams, and the like. Contact may beaccomplished through use of infusers, bubblers, fluidic Venturireactors, spargers, gas filters, sprays, trays, or packed columnreactors, and the like, as may be convenient. The process may be a batchor continuous process.

In some instances, the gaseous source of CO₂ is contacted with theliquid using a microporous membrane contactor. Microporous membranecontactors of interest include a microporous membrane present in asuitable housing, where the housing includes a gas inlet and a liquidinlet, as well a gas outlet and a liquid outlet. The contactor isconfigured so that the gas and liquid contact opposite sides of themembrane in a manner such that molecule may dissolve into the liquidfrom the gas via the pores of the microporous membrane. The membrane maybe configured in any convenient format, where in some instances themembrane is configured in a hollow fiber format. Hollow fiber membranereactor formats which may be employed include, but are not limited to,those described in U.S. Pat. Nos. 7,264,725; 6,872,240 and 5,695,545;the disclosures of which are herein incorporated by reference. In someinstances, the microporous hollow fiber membrane contactor that isemployed is a Liqui-Cel® hollow fiber membrane contactor (available fromMembrana, Charlotte N.C.), which membrane contactors includepolypropylene membrane contactors and polyolefin membrane contactors.

Contact between the capture liquid and the CO₂-containing gas occursunder conditions such that a substantial portion of the CO₂ present inthe CO₂-containing gas goes into solution, e.g., to produce bicarbonateions. By substantial portion is meant 10% or more, such as 50% or more,including 80% or more.

The temperature of the capture liquid that is contacted with theCO₂-containing gas may vary. In some instances, the temperature rangesfrom −1.4 to 100° C., such as 20 to 80° C. and including 40 to 70° C. Insome instances, the temperature may range from −1.4 to 50° C. or higher,such as from −1.1 to 45° C. or higher. In some instances, coolertemperatures are employed, where such temperatures may range from −1.4to 4° C., such as −1.1 to 0° C. In some instances, warmer temperaturesare employed. For example, the temperature of the capture liquid in someinstances may be 25° C. or higher, such as 30° C. or higher, and may insome embodiments range from 25 to 50° C., such as 30 to 40° C.

The CO₂-containing gas and the capture liquid are contacted at apressure suitable for production of a desired CO₂ charged liquid. Insome instances, the pressure of the contact conditions is selected toprovide for optimal CO₂ absorption, where such pressures may range from1 ATM to 100 ATM, such as 1 to 50 ATM, e.g., 20-30 ATM or 1 ATM to 10ATM. Where contact occurs at a location that is naturally at 1 ATM, thepressure may be increased to the desired pressure using any convenientprotocol. In some instances, contact occurs where the optimal pressureis present, e.g., at a location under the surface of a body of water,such as an ocean or sea. In some instances, contact of theCO₂-containing gas and the alkaline aqueous medium occurs a depth belowthe surface of the water (e.g., the surface of the ocean), where thedepth may range in some instances from 10 to 1000 meters, such as 10 to100 meters. In some instances, the CO₂ containing gas and CO₂ captureliquid are contacted at a pressure that provides for selectiveabsorption of CO₂ from the gas, relative to other gases in the CO₂containing gas, such as N₂, etc. In these instances, the pressure atwhich the CO₂ containing gas and capture liquid are contacted may vary,ranging from 1 to 100 atmospheres (atm), such as 1 to 10 atm andincluding 20 to 50 atm.

The gaseous source of CO₂ is contacted with the aqueous capture ammoniain manner sufficient to produce an aqueous ammonium carbonate. Theaqueous ammonium carbonate may vary, where in some instances the aqueousammonium carbonate comprises at least one of ammonium carbonate andammonium bicarbonate and in some instances comprises both ammoniumcarbonate and ammonium bicarbonate. The aqueous ammonium bicarbonate maybe viewed as a DIC containing liquid. As such, in charging the aqueouscapture ammonia with CO₂, a CO₂ containing gas may be contacted with CO₂capture liquid under conditions sufficient to produce dissolvedinorganic carbon (DIC) in the CO₂ capture liquid, i.e., to produce a DICcontaining liquid. The DIC is the sum of the concentrations of inorganiccarbon species in a solution, represented by the equation:DIC=[CO₂*]+[HCO₃ ⁻]+[CO₃ ²⁻], where [CO₂*] is the sum of carbon dioxide([CO₂]) and carbonic acid ([H₂CO₃]) concentrations,

[HCO₃ ⁻] is the bicarbonate concentration (which includes ammoniumbicarbonate) and [CO₃ ²⁻] is the carbonate concentration (which includesammonium carbonate) in the solution. The DIC of the aqueous media mayvary, and in some instances may be 5,000 ppm or greater, such as 10,000ppm or greater, including 15,000 ppm or greater. In some instances, theDIC of the aqueous media may range from 5,000 to 20,000 ppm, such as7,500 to 15,000 ppm, including 8,000 to 12,000 ppm. The amount of CO₂dissolved in the liquid may vary, and in some instances ranges from 0.05to 40 mM, such as 1 to 35 mM, including 25 to 30 mM. The pH of theresultant DIC containing liquid may vary, ranging in some instances from4 to 12, such as 6 to 11 and including 7 to 10, e.g., 8 to 8.5.

In some instances where the gaseous source of CO₂ is a multicomponentgaseous stream, contact occurs in a manner such that such that CO₂ isselectively absorbed by the CO₂ absorbing aqueous medium. By selectivelyabsorbed is meant that the CO₂ molecules preferentially go into solutionrelative to other molecules in the multi-component gaseous stream, suchas N₂, O₂, Ar, CO, H₂, CH₄ and the like.

Where desired, the CO₂ containing gas is contacted with the captureliquid in the presence of a catalyst (i.e., an absorption catalyst,either hetero- or homogeneous in nature) that mediates the conversion ofCO₂ to bicarbonate. Of interest as absorption catalysts are catalyststhat, at pH levels ranging from 8 to 10, increase the rate of productionof bicarbonate ions from dissolved CO₂. The magnitude of the rateincrease (e.g., as compared to control in which the catalyst is notpresent) may vary, and in some instances is 2-fold or greater, such as5-fold or greater, e.g., 10-fold or greater, as compared to a suitablecontrol. Further details regarding examples of suitable catalysts forsuch embodiments are found in U.S. patent application Ser. No.14/636,043, the disclosure of which is herein incorporated by reference.

In some embodiments, the resultant aqueous ammonium carbonate is a twophase liquid which includes droplets of a liquid condensed phase (LCP)in a bulk liquid, e.g., bulk solution. By “liquid condensed phase” or“LCP” is meant a phase of a liquid solution which includes bicarbonateions wherein the concentration of bicarbonate ions is higher in the LCPphase than in the surrounding, bulk liquid. LCP droplets arecharacterized by the presence of a meta-stable bicarbonate-rich liquidprecursor phase in which bicarbonate ions associate into condensedconcentrations exceeding that of the bulk solution and are present in anon-crystalline solution state. The LCP contains all of the componentsfound in the bulk solution that is outside of the interface. However,the concentration of the bicarbonate ions is higher than in the bulksolution. In those situations where LCP droplets are present, the LCPand bulk solution may each contain ion-pairs and pre-nucleation clusters(PNCs). When present, the ions remain in their respective phases forlong periods of time, as compared to ion-pairs and PNCs in solution.Further details regarding LCP containing liquids are provided in U.S.patent application Ser. No. 14/636,043, the disclosure of which isherein incorporated by reference.

Production of Solid CO₂ Sequestering Carbonate

Following production of an aqueous ammonium carbonate, e.g., asdescribed above, the aqueous ammonium carbonate is combined with acation source under conditions sufficient to produce a solid CO₂sequestering carbonate and an aqueous ammonium salt. Cations ofdifferent valances can form solid carbonate compositions (e.g., in theform of carbonate minerals). In some instances, monovalent cations, suchas sodium and potassium cations, may be employed. In other instances,divalent cations, such as alkaline earth metal cations, e.g., calciumand magnesium cations, may be employed. When cations are added to theaqueous ammonium carbonate, precipitation of carbonate solids, such asamorphous calcium carbonate when the divalent cations include Ca²⁺, maybe produced with a stoichiometric ratio of one carbonate-species ion percation.

Any convenient cation source may be employed in such instances. Cationsources of interest include, but are not limited to, the brine fromwater processing facilities such as sea water desalination plants,brackish water desalination plants, groundwater recovery facilities,wastewater facilities, and the like, which produce a concentrated streamof solution high in cation contents. Also of interest as cation sourcesare naturally occurring sources, such as but not limited to nativeseawater and geological brines, which may have varying cationconcentrations and may also provide a ready source of cations to triggerthe production of carbonate solids from the aqueous ammonium carbonate.In some instances, the cation source may be a waste product of anotherstep of the process, e.g., a calcium salt (such as CaCl₂) producedduring regeneration of ammonia from the aqueous ammonium salt.

The product carbonate compositions may vary greatly. The precipitatedproduct may include one or more different carbonate compounds, such astwo or more different carbonate compounds, e.g., three or more differentcarbonate compounds, five or more different carbonate compounds, etc.,including non-distinct, amorphous carbonate compounds. Carbonatecompounds of precipitated products of the invention may be compoundshaving a molecular formulation X_(m)(CO₃)_(n) where X is any element orcombination of elements that can chemically bond with a carbonate groupor its multiple, wherein X is in certain embodiments an alkaline earthmetal and not an alkali metal; wherein m and n are stoichiometricpositive integers. These carbonate compounds may have a molecularformula of X_(m)(CO₃)_(n).H₂O, where there are one or more structuralwaters in the molecular formula. The amount of carbonate in the product,as determined by coulometry using the protocol described as coulometrictitration, may be 40% or higher, such as 70% or higher, including 80% orhigher.

The carbonate compounds of the precipitated products may include anumber of different cations, such as but not limited to ionic speciesof: calcium, magnesium, sodium, potassium, sulfur, boron, silicon,strontium, and combinations thereof. Of interest are carbonate compoundsof divalent metal cations, such as calcium and magnesium carbonatecompounds. Specific carbonate compounds of interest include, but are notlimited to: calcium carbonate minerals, magnesium carbonate minerals andcalcium magnesium carbonate minerals. Calcium carbonate minerals ofinterest include, but are not limited to: calcite (CaCO₃), aragonite(CaCO₃), vaterite (CaCO₃), ikaite (CaCO₃.6H₂O), and amorphous calciumcarbonate (CaCO₃). Magnesium carbonate minerals of interest include, butare not limited to magnesite (MgCO₃), barringtonite (MgCO₃.2H₂O),nesquehonite (MgCO₃.3H₂O), lanfordite (MgCO₃.5H₂O), hydromagnisite, andamorphous magnesium calcium carbonate (MgCO₃). Calcium magnesiumcarbonate minerals of interest include, but are not limited to dolomite(CaMg)(CO₃)₂), huntite (Mg₃Ca(CO₃)₄) and sergeevite(Ca₂Mg₁₁(CO₃)₁₃.H₂O). The carbonate compounds of the product may includeone or more waters of hydration, or may be anhydrous. In some instances,the amount by weight of magnesium carbonate compounds in the precipitateexceeds the amount by weight of calcium carbonate compounds in theprecipitate. For example, the amount by weight of magnesium carbonatecompounds in the precipitate may exceed the amount by weight calciumcarbonate compounds in the precipitate by 5% or more, such as 10% ormore, 15% or more, 20% or more, 25% or more, 30% or more. In someinstances, the weight ratio of magnesium carbonate compounds to calciumcarbonate compounds in the precipitate ranges from 1.5-5 to 1, such as2-4 to 1 including 2-3 to 1. In some instances, the precipitated productmay include hydroxides, such as divalent metal ion hydroxides, e.g.,calcium and/or magnesium hydroxides.

Further details regarding carbonate production and methods of using thecarbonated produced thereby are provided in U.S. application Ser. Nos.14/112,495; 14/204,994; 14/214,129; 14/214,130; 14/636,043 and14/861,996; as well as PCT Application Serial No. PCT/US2015/054547; thedisclosures of which are herein incorporated by reference.

In some instances, carbonate production occurs in a continuous fashion,e.g., as described in Ser. No. 14/877,766, the disclosure of which isherein incorporated by reference. In some such instances, carbonateproduction may occur in the presence of a seed structure. By seedstructure is meant a solid structure or material that is present flowingliquid, e.g., in the material production zone, prior to divalent cationintroduction into the liquid. By “in association with” is meant that thematerial is produced on at least one of a surface of or in a depression,e.g., a pore, crevice, etc., of the seed structure. In such instances, acomposite structure of the carbonate material and the seed structure isproduced. In some instances, the product carbonate material coats aportion, if not all of, the surface of a seed structure. In someinstances, the product carbonate materials fills in a depression of theseed structure, e.g., a pore, crevice, fissure, etc.

Seed structures may vary widely as desired. The term “seed structure” isused to describe any object upon and/or in which the product carbonatematerial forms. Seed structures may range from singular objects orparticulate compositions, as desired. Where the seed structure is asingular object, it may have a variety of different shapes, which may beregular or irregular, and a variety of different dimensions. Shapes ofinterest include, but are not limited to, rods, meshes, blocks, etc.Also of interest are particulate compositions, e.g., granularcompositions, made up of a plurality of particles. Where the seedstructure is a particulate composition, the dimensions of particles mayvary, ranging in some instances from 0.01 to 1,000,000 μm, such as 0.1to 100,000 μm.

The seed structure may be made up of any convenient material ormaterials. Materials of interest include both carbonate materials, suchas described above, as well as non-carbonate materials. The seedstructures may be naturally occurring, e.g., naturally occurring sands,shell fragments from oyster shells or other carbonate skeletalallochems, gravels, etc., or man-made, such as pulverized rocks, groundblast furnace slag, fly ash, cement kiln dust, red mud, and the like.For example, the seed structure may be a granular composition, such assand, which is coated with the carbonate material during the process,e.g., a white carbonate material or colored carbonate material, e.g., asdescribed above.

In some instances, seed structure may be coarse aggregates, such asfriable Pleistocene coral rock, e.g., as may be obtained from tropicalareas (e.g., Florida) that are too weak to serve as aggregate forconcrete. In this case the friable coral rock can be used as a seed, andthe solid CO₂ sequestering carbonate mineral may be deposited in theinternal pores, making the coarse aggregate suitable for use inconcrete, allowing it to pass the LA Rattler abrasion test. In someinstances, where a light weight aggregate is desired, the outer surfacewill only be penetrated by the solution of deposition, leaving the innercore relatively ‘hollow’ making a light weight aggregate for use inlight weight concrete.

Production of Materials from the CO₂ Sequestering Carbonate Product

The product carbonate material may be further used, manipulated and/orcombined with other compositions to produce a variety of end-usematerials. In certain embodiments, the product carbonate composition isrefined (i.e., processed) in some manner. Refinement may include avariety of different protocols. In certain embodiments, the product issubjected to mechanical refinement, e.g., grinding, in order to obtain aproduct with desired physical properties, e.g., particle size, etc. Incertain embodiments, the product is combined with a hydraulic cement,e.g., as a sand, a gravel, as an aggregate, etc., e.g., to produce finalproduct, e.g., concrete or mortar.

Also of interest are formed building materials. The formed buildingmaterials of the invention may vary greatly. By “formed” is meantshaped, e.g., molded, cast, cut or otherwise produced, into a man-madestructure defined physical shape, i.e., configuration. Formed buildingmaterials are distinct from amorphous building materials, e.g.,particulate (such as powder) compositions that do not have a defined andstable shape, but instead conform to the container in which they areheld, e.g., a bag or other container. Illustrative formed buildingmaterials include, but are not limited to: bricks; boards; conduits;beams; basins; columns; drywalls etc. Further examples and detailsregarding formed building materials include those described in UnitedStates Published Application No. US20110290156; the disclosure of whichis herein incorporated by reference.

Also of interest are non-cementitious manufactured items that includethe product of the invention as a component. Non-cementitiousmanufactured items of the invention may vary greatly. Bynon-cementitious is meant that the compositions are not hydrauliccements. As such, the compositions are not dried compositions that, whencombined with a setting fluid, such as water, set to produce a stableproduct. Illustrative compositions include, but are not limited to:paper products; polymeric products; lubricants; asphalt products;paints; personal care products, such as cosmetics, toothpastes,deodorants, soaps and shampoos; human ingestible products, includingboth liquids and solids; agricultural products, such as soil amendmentproducts and animal feeds; etc. Further examples and detailsnon-cementitious manufactured items include those described in U.S. Pat.No. 7,829,053; the disclosure of which is herein incorporated byreference.

Aggregates

As summarized above, the methods and systems of the invention may beemployed to produce carbonate coated aggregates, e.g., for use inconcretes and other applications. The carbonate coated aggregates may beconventional or lightweight aggregates.

Aspects of the invention include CO₂ sequestering aggregatecompositions. The CO₂ sequestering aggregate compositions includeaggregate particles having a core and a CO₂ sequestering carbonatecoating on at least a portion of a surface of the core. The CO₂sequestering carbonate coating is made up of a CO₂ sequesteringcarbonate material, e.g., as described above. The CO₂ sequesteringcarbonate material that is present in coatings of the coated particlesof the subject aggregate compositions may vary. In some instances, theisotopic profile of the core of the aggregate differs from the carbonatecoating of the aggregate, such that the aggregate has a carbonatecoating with a first isotopic profile and a core with a second isotopicprofile that is different from the first.

In some instances, the carbonate material is a highly reflectivemicrocrystalline/amorphous carbonate material. Themicrocrystalline/amorphous materials present in coatings of theinvention may be highly reflective. As the materials may be highlyreflective, the coatings that include the same may have a high totalsurface reflectance (TSR) value. TSR may be determined using anyconvenient protocol, such as ASTM E1918 Standard Test Method forMeasuring Solar Reflectance of Horizontal and Low-Sloped Surfaces in theField (see also R. Levinson, H. Akbari, P. Berdahl, Measuring solarreflectance—Part II: review of practical methods, LBNL 2010). In someinstances, the backsheets exhibit a TSR value ranging from Rg;0=0.0 toRg;0,=1.0, such as Rg;0,=0.25 to Rg;0,=0.99, including Rg;0,=0.40 toRg;0,=0.98, e.g., as measured using the protocol referenced above.

In some instances, the coatings that include the carbonate materials arehighly reflective of near infra-red (NIR) light, ranging in someinstances from 10 to 99%, such as 50 to 99%. By NIR light is meant lighthaving a wavelength ranging from 700 nanometers (nm) to 2.5 mm. NIRreflectance may be determined using any convenient protocol, such asASTM C1371-04a(2010)e1 Standard Test Method for Determination ofEmittance of Materials Near Room Temperature Using Portable Emissometers(http://www.astm.org/Standards/C1371.htm) or ASTM G173-03(2012) StandardTables for Reference Solar Spectral Irradiances: Direct Normal andHemispherical on 37° Tilted Surface(http://rredc.nrel.gov/solar/spectra/am1.5/ASTMG173/ASTMG173.html). Insome instances, the coatings exhibit a NIR reflectance value rangingfrom Rg;0=0.0 to Rg;0=1.0, such as Rg;0=0.25 to Rg;0=0.99, includingRg;0=0.40 to Rg;0=0.98, e.g., as measured using the protocol referencedabove.

In some instances, the carbonate coatings are highly reflective ofultra-violet (UV) light, ranging in some instances from 10 to 99%, suchas 50 to 99%. By UV light is meant light having a wavelength rangingfrom 400 nm and 10 nm. UV reflectance may be determined using anyconvenient protocol, such as ASTM G173-03(2012) Standard Tables forReference Solar Spectral Irradiances: Direct Normal and Hemispherical on37° Tilted Surface. In some instances, the materials exhibit a UV valueranging from Rg;0=0.0 to Rg;0=1.0, such as Rg;0=0.25 to Rg;0=0.99,including Rg;0=0.4 to Rg;0=0.98, e.g., as measured using the protocolreferenced above.

In some instances, the coatings are reflective of visible light, e.g.,where reflectivity of visible light may vary, ranging in some instancesfrom 10 to 99%, such as 10 to 90%. By visible light is meant lighthaving a wavelength ranging from 380 nm to 740 nm. Visible lightreflectance properties may be determined using any convenient protocol,such as ASTM G173-03(2012) Standard Tables for Reference Solar SpectralIrradiances: Direct Normal and Hemispherical on 37° Tilted Surface. Insome instances, the coatings exhibit a visible light reflectance valueranging from Rg;0=0.0 to Rg;0=1.0, such as Rg;0=0.25 to Rg;0=0.99,including Rg;0=0.4 to Rg;0=0.98, e.g., as measured using the protocolreferenced above.

The materials making up the carbonate components are, in some instances,amorphous or microcrystalline. Where the materials are microcrystalline,the crystal size, e.g., as determined using the Scherrer equationapplied to the FWHM of X-ray diffraction pattern, is small, and in someinstances is 1000 microns or less in diameter, such as 100 microns orless in diameter, and including 10 microns or less in diameter. In someinstances, the crystal size ranges in diameter from 1000 μm to 0.001 μm,such as 10 to 0.001 μm, including 1 to 0.001 μm. In some instances, thecrystal size is chosen in view of the wavelength(s) of light that are tobe reflected. For example, where light in the visible spectrum is to bereflected, the crystal size range of the materials may be selected to beless than one-half the “to be reflected” range, so as to give rise tophotonic band gap. For example, where the to be reflected wavelengthrange of light is 100 to 1000 nm, the crystal size of the material maybe selected to be 50 nm or less, such as ranging from 1 to 50 nm, e.g.,5 to 25 nm. In some embodiments, the materials produced by methods ofthe invention may include rod-shaped crystals and amorphous solids. Therod-shaped crystals may vary in structure, and in certain embodimentshave length to diameter ratio ranging from 500 to 1, such as 10 to 1. Incertain embodiments, the length of the crystals ranges from 0.5 μm to500 μm, such as from 5 μm to 100 μm. In yet other embodiments,substantially completely amorphous solids are produced.

The density, porosity, and permeability of the coating materials mayvary according to the application. With respect to density, while thedensity of the material may vary, in some instances the density rangesfrom 5 g/cm³ to 0.01 g/cm³, such as 3 g/cm³ to 0.3 g/cm³ and including2.7 g/cm³ to 0.4 g/cm³. With respect to porosity, as determined by GasSurface Adsorption as determined by the BET method (Brown

Emmett Teller (e.g., as described athttp://en.wikipedia.org/wiki/BET_theory, S. Brunauer, P. H. Emmett andE. Teller, J. Am. Chem. Soc., 1938, 60, 309. doi:10.1021/ja01269a023)the porosity may range in some instances from 100 m²/g to 0.1 m²/g, suchas 60 m²/g to 1 m²/g and including 40 m²/g to 1.5 m²/g. With respect topermeability, in some instances the permeability of the material mayrange from 0.1 to 100 darcies, such as 1 to 10 darcies, including 1 to 5darcies (e.g., as determined using the protocol described in H. Darcy,Les Fontaines Publiques de la Ville de Dijon, Dalmont, Paris (1856).).Permeability may also be characterized by evaluating water absorption ofthe material. As determined by water absorption protocol, e.g., thewater absorption of the material ranges, in some embodiments, from 0 to25%, such as 1 to 15% and including from 2 to 9%.

The hardness of the materials may also vary. In some instances, thematerials exhibit a Mohs hardness of 3 or greater, such as 5 or greater,including 6 or greater, where the hardness ranges in some instances from3 to 8, such as 4 to 7 and including 5 to 6 Mohs (e.g., as determinedusing the protocol described in American Federation of MineralogicalSocieties. “Mohs Scale of Mineral Hardness”). Hardness may also berepresented in terms of tensile strength, e.g., as determined using theprotocol described in ASTM C1167. In some such instances, the materialmay exhibit a compressive strength of 100 to 3000 N, such as 400 to 2000N, including 500 to 1800 N.

In some embodiments, a the carbonate material includes one or morecontaminants predicted not to leach into the environment by one or moretests selected from the group consisting of Toxicity CharacteristicLeaching Procedure, Extraction Procedure Toxicity Test, SyntheticPrecipitation Leaching Procedure, California Waste Extraction Test,Soluble Threshold Limit Concentration, American Society for Testing andMaterials Extraction Test, and Multiple Extraction Procedure. Tests andcombinations of tests may be chosen depending upon likely contaminantsand storage conditions of the composition. For example, in someembodiments, the composition may include As, Cd, Cr, Hg, and Pb (orproducts thereof), each of which might be found in a waste gas stream ofa coal-fired power plant. Since TCLP tests for As, Ba, Cd, Cr, Pb, Hg,Se, and Ag, TCLP may be an appropriate test for aggregates describedherein. In some embodiments, a carbonate composition of the inventionincludes As, wherein the composition is predicted not to leach As intothe environment. For example, a TCLP extract of the composition mayprovide less than 5.0 mg/L As indicating that the composition is nothazardous with respect to As. In some embodiments, a carbonatecomposition of the invention includes Cd, wherein the composition ispredicted not to leach Cd into the environment. For example, a TCLPextract of the composition may provide less than 1.0 mg/L Cd indicatingthat the composition is not hazardous with respect to Cd. In someembodiments, a carbonate composition of the invention includes Cr,wherein the composition is predicted not to leach Cr into theenvironment. For example, a TCLP extract of the composition may provideless than 5.0 mg/L Cr indicating that the composition is not hazardouswith respect to Cr. In some embodiments, a carbonate composition of theinvention includes Hg, wherein the composition is predicted not to leachHg into the environment. For example, a TCLP extract of the compositionmay provide less than 0.2 mg/L Hg indicating that the composition is nothazardous with respect to Hg. In some embodiments, a carbonatecomposition of the invention includes Pb, wherein the composition ispredicted not to leach Pb into the environment. For example, a TCLPextract of the composition may provide less than 5.0 mg/L Pb indicatingthat the composition is not hazardous with respect to Pb. In someembodiments, a carbonate composition and aggregate that includes of thesame of the invention may be non-hazardous with respect to a combinationof different contaminants in a given test. For example, the carbonatecomposition may be non-hazardous with respect to all metal contaminantsin a given test. A TCLP extract of a composition, for instance, may beless than 5.0 mg/L in As, 100.0 mg/L in Ba, 1.0 mg/L in Cd, 5.0 mg/mL inCr, 5.0 mg/L in Pb, 0.2 mg/L in Hg, 1.0 mg/L in Se, and 5.0 mg/L in Ag.Indeed, a majority if not all of the metals tested in a TCLP analysis ona composition of the invention may be below detection limits. In someembodiments, a carbonate composition of the invention may benon-hazardous with respect to all (e.g., inorganic, organic, etc.)contaminants in a given test. In some embodiments, a carbonatecomposition of the invention may be non-hazardous with respect to allcontaminants in any combination of tests selected from the groupconsisting of Toxicity Characteristic Leaching Procedure, ExtractionProcedure Toxicity Test, Synthetic Precipitation Leaching Procedure,California Waste Extraction Test, Soluble Threshold Limit Concentration,American Society for Testing and Materials Extraction Test, and MultipleExtraction Procedure. As such, carbonate compositions and aggregatesincluding the same of the invention may effectively sequester CO₂ (e.g.,as carbonates, bicarbonates, or a combinations thereof) along withvarious chemical species (or co-products thereof) from waste gasstreams, industrial waste sources of divalent cations, industrial wastesources of proton-removing agents, or combinations thereof that might beconsidered contaminants if released into the environment. Compositionsof the invention incorporate environmental contaminants (e.g., metalsand co-products of metals such as Hg, Ag, As, Ba, Be, Cd, Co, Cr, Cu,Mn, Mo, Ni, Pb, Sb, Se, TI, V, Zn, or combinations thereof) in anon-leachable form.

The aggregate compositions of the invention include particles having acore region and a CO₂ sequestering carbonate coating on at least aportion of a surface of the core. The coating may cover 10% or more, 20%or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% ormore, 80% or more, 90% or more, including 95% or more of the surface ofthe core. The thickness of the carbonate layer may vary, as desired. Insome instances, the thickness may range from 0.1 μm to 10 mm, such as 1μm to 1000 μm, including 10 μm to 500 μm.

The core of the coated particles of the aggregate compositions describedherein may vary widely. The core may be made up of any convenientaggregate material. Examples of suitable aggregate materials include,but are not limited to: natural mineral aggregate materials, e.g.,carbonate rocks, sand (e.g., natural silica sand), sandstone, gravel,granite, diorite, gabbro, basalt, etc.; and synthetic aggregatematerials, such as industrial byproduct aggregate materials, e.g.,blast-furnace slag, fly ash, municipal waste, and recycled concrete,etc. In some instances, the core comprises a material that is differentfrom the carbonate coating.

In some instances, the aggregates are lightweight aggregates. In suchinstances, the core of the coated particles of the aggregatecompositions described herein may vary widely, so long as when it iscoated it provides for the desired lightweight aggregate composition.The core may be made up of any convenient material. Examples of suitableaggregate materials include, but are not limited to: conventionallightweight aggregate materials, e.g., naturally occurring lightweightaggregate materials, such as crushed volcanic rocks, e.g., pumice,scoria or tuff, and synthetic materials, such as thermally treatedclays, shale, slate, diatomite, perlite, vermiculite, blast-furnace slagand fly ash; as well as unconventional porous materials, e.g., crushedcorals, synthetic materials like polymers and low density polymericmaterials, recycled wastes such as wood, fibrous materials, cement kilndust residual materials, recycled glass, various volcanic minerals,granite, silica bearing minerals, mine tailings and the like.

The physical properties of the coated particles of the aggregatecompositions may vary. Aggregates of the invention have a density thatmay vary so long as the aggregate provides the desired properties forthe use for which it will be employed, e.g., for the building materialin which it is employed. In certain instances, the density of theaggregate particles ranges from 1.1 to 5 gm/cc, such as 1.3 gm/cc to3.15 gm/cc, and including 1.8 gm/cc to 2.7 gm/cc. Other particledensities in embodiments of the invention, e.g., for lightweightaggregates, may range from 1.1 to 2.2 gm/cc, e.g., 1.2 to 2.0 g/cc or1.4 to 1.8 g/cc. In some embodiments the invention provides aggregatesthat range in bulk density (unit weight) from 50 lb/lb/ft³ to 200lb/ft³, or 75 lb/ft³ to 175 lb/ft³, or 50 lb/ft³ to 100 lb/ft³, or 75lb/ft³ to 125 lb/ft³, or lb/ft³ to 115 lb/ft³, or 100 lb/ft³ to 200lb/ft³, or 125 lb/ft³ to lb/ft³, or 140 lb/ft³ to 160 lb/ft³, or 50lb/ft³ to 200 lb/ft³. Some embodiments of the invention providelightweight aggregate, e.g., aggregate that has a bulk density (unitweight) of 75 lb/ft³ to 125 lb/ft³, such as 90 lb/ft³ to 115 lb/ft³. Insome instances, the lightweight aggregates have a weight ranging from 50to 1200 kg/m³, such as 80 to 11 kg/m³.

The hardness of the aggregate particles making up the aggregatecompositions of the invention may also vary, and in certain instancesthe hardness, expressed on the Mohs scale, ranges from 1.0 to 9, such as1 to 7, including 1 to 6 or 1 to 5. In some embodiments, the Mohr'shardness of aggregates of the invention ranges from 2-5, or 2-4. In someembodiments, the Mohs hardness ranges from 2-6. Other hardness scalesmay also be used to characterize the aggregate, such as the Rockwell,Vickers, or Brinell scales, and equivalent values to those of the Mohsscale may be used to characterize the aggregates of the invention; e.g.,a Vickers hardness rating of 250 corresponds to a Mohs rating of 3;conversions between the scales are known in the art.

The abrasion resistance of an aggregate may also be important, e.g., foruse in a roadway surface, where aggregates of high abrasion resistanceare useful to keep surfaces from polishing. Abrasion resistance isrelated to hardness but is not the same.

Aggregates of the invention include aggregates that have an abrasionresistance similar to that of natural limestone, or aggregates that havean abrasion resistance superior to natural limestone, as well asaggregates having an abrasion resistance lower than natural limestone,as measured by art accepted methods, such as ASTM C131-03. In someembodiments aggregates of the invention have an abrasion resistance ofless than 50%, or less than 40%, or less than 35%, or less than 30%, orless than 25%, or less than 20%, or less than 15%, or less than 10%,when measured by ASTM C131-03.

Aggregates of the invention may also have a porosity within a particularranges. As will be appreciated by those of skill in the art, in somecases a highly porous aggregate is desired, in others an aggregate ofmoderate porosity is desired, while in other cases aggregates of lowporosity, or no porosity, are desired. Porosities of aggregates of someembodiments of the invention, as measured by water uptake after ovendrying followed by full immersion for 60 minutes, expressed as % dryweight, can be in the range of 1-40%, such as 2-20%, or 2-15%, including2-10% or even 3-9%.

The dimensions of the aggregate particles may vary. Aggregatecompositions of the invention are particulate compositions that may insome embodiments be classified as fine or coarse. Fine aggregatesaccording to embodiments of the invention are particulate compositionsthat almost entirely pass through a Number 4 sieve (ASTM C 125 and ASTMC 33). Fine aggregate compositions according to embodiments of theinvention have an average particle size ranging from 10 μm to 4.75 mm,such as 50 μm to 3.0 mm and including 75 μm to 2.0 mm. Coarse aggregatesof the invention are compositions that are predominantly retained on aNumber 4 sieve (ASTM C 125 and ASTM C 33). Coarse aggregate compositionsaccording to embodiments of the invention are compositions that have anaverage particle size ranging from 4.75 mm to 200 mm, such as 4.75 to150 mm in and including 5 to 100 mm. As used herein, “aggregate” mayalso in some embodiments encompass larger sizes, such as 3 in to 12 inor even 3 in to 24 in, or larger, such as 12 in to 48 in, or larger than48 in.

Concrete Dry Composites

Also provided are concrete dry composites that, upon combination with asuitable setting liquid (such as described below), produce a settablecomposition that sets and hardens into a concrete or a mortar. Concretedry composites as described herein include an amount of an aggregate,e.g., as described above, and a cement, such as a hydraulic cement. Theterm “hydraulic cement” is employed in its conventional sense to referto a composition which sets and hardens after combining with water or asolution where the solvent is water, e.g., an admixture solution.Setting and hardening of the product produced by combination of theconcrete dry composites of the invention with an aqueous liquid resultsfrom the production of hydrates that are formed from the cement uponreaction with water, where the hydrates are essentially insoluble inwater.

Aggregates of the invention find use in place of conventional naturalrock aggregates used in conventional concrete when combined with purePortland cement. Other hydraulic cements of interest in certainembodiments are Portland cement blends. The phrase “Portland cementblend” includes a hydraulic cement composition that includes a Portlandcement component and significant amount of a non-Portland cementcomponent. As the cements of the invention are Portland cement blends,the cements include a Portland cement component. The Portland cementcomponent may be any convenient Portland cement. As is known in the art,Portland cements are powder compositions produced by grinding Portlandcement clinker (more than 90%), a limited amount of calcium sulfatewhich controls the set time, and up to 5% minor constituents (as allowedby various standards). When the exhaust gases used to provide carbondioxide for the reaction contain SOx, then sufficient sulphate may bepresent as calcium sulfate in the precipitated material, either as acement or aggregate to off set the need for additional calcium sulfate.As defined by the European Standard EN197.1, “Portland cement clinker isa hydraulic material which shall consist of at least two-thirds by massof calcium silicates (3CaO.SiO₂ and 2CaO.SiO₂), the remainder consistingof aluminium- and iron-containing clinker phases and other compounds.The ratio of CaO to SiO₂ shall not be less than 2.0. The magnesiumcontent (MgO) shall not exceed 5.0% by mass.” The concern about MgO isthat later in the setting reaction, magnesium hydroxide, brucite, mayform, leading to the deformation and weakening and cracking of thecement. In the case of magnesium carbonate containing cements, brucitewill not form as it may with MgO. In certain embodiments, the Portlandcement constituent of the present invention is any Portland cement thatsatisfies the ASTM Standards and Specifications of C150 (Types I-VIII)of the American Society for Testing of Materials (ASTM C50-StandardSpecification for Portland Cement). ASTM C150 covers eight types ofPortland cement, each possessing different properties, and usedspecifically for those properties.

Also of interest as hydraulic cements are carbonate containing hydrauliccements. Such carbonate containing hydraulic cements, methods for theirmanufacture and use are described in U.S. Pat. No. 7,735,274; thedisclosure of which applications are herein incorporated by reference.

In certain embodiments, the hydraulic cement may be a blend of two ormore different kinds of hydraulic cements, such as Portland cement and acarbonate containing hydraulic cement. In certain embodiments, theamount of a first cement, e.g., Portland cement in the blend ranges from10 to 90% (w/w), such as 30 to 70% (w/w) and including 40 to 60% (w/w),e.g., a blend of 80% OPC and 20% carbonate hydraulic cement.

In some instances, the concrete dry composite compositions, as well asconcretes produced therefrom, have a CarbonStar Rating (CSR) that isless than the CSR of the control composition that does not include anaggregate of the invention. The Carbon Star Rating (CSR) is a value thatcharacterizes the embodied carbon (in the form of CaCO₃) for anyproduct, in comparison to how carbon intensive production of the productitself is (i.e., in terms of the production CO₂). The CSR is a metricbased on the embodied mass of CO₂ in a unit of concrete. Of the threecomponents in concrete-water, cement and aggregate-cement is by far themost significant contributor to CO₂ emissions, roughly 1:1 by mass (1ton cement produces roughly 1 ton CO2). So, if a cubic yard of concreteuses 600 lb cement, then its CSR is 600. A cubic yard of concreteaccording to embodiments of the present invention which include 600 lbcement and in which at least a portion of the aggregate is carbonatecoated aggregate, e.g., as described above, will have a CSR that is lessthan 600, e.g., where the CSR may be 550 or less, such as 500 or less,including 400 or less, e.g., 250 or less, such as 100 or less, where insome instances the CSR may be a negative value, e.g., −100 or less, suchas −500 or less including −1000 or less, where in some instances the CSRof a cubic yard of concrete having 600 lbs cement may range from 500 to−5000, such as −100 to −4000, including −500 to −3000. To determine theCSR of a given cubic yard of concrete that includes carbonate coatedaggregate of the invention, an initial value of CO₂ generated for theproduction of the cement component of the concrete cubic yard isdetermined. For example, where the yard includes 600 lbs of cement, theinitial value of 600 is assigned to the yard. Next, the amount ofcarbonate coating in the yard is determined. Since the molecular weightof carbonate is 100 a.u., and 44% of carbonate is CO₂, the amount ofcarbonate coating is present in the yard is then multiplied by 0.44 andthe resultant value subtracted from the initial value in order to obtainthe CSR for the yard. For example, where a given yard of concrete mix ismade up of 600 lbs of cement, 300 lbs of water, 1429 lbs of fineaggregate and 1739 lbs of coarse aggregate, the weight of a yard ofconcrete is 4068 lbs and the CSR is 600. If 10% of the total mass ofaggregate in this mix is replaced by carbonate coating, e.g., asdescribed above, the amount of carbonate present in the revised yard ofconcrete is 317 lbs. Multiplying this value by 0.44 yields 139.5.Subtracting this number from 600 provides a CSR of 460.5.

Settable Compositions

Settable compositions of the invention, such as concretes and mortars,are produced by combining a hydraulic cement with an amount of aggregate(fine for mortar, e.g., sand; coarse with or without fine for concrete)and an aqueous liquid, e.g., water, either at the same time or bypre-combining the cement with aggregate, and then combining theresultant dry components with water. The choice of coarse aggregatematerial for concrete mixes using cement compositions of the inventionmay have a minimum size of about ⅜ inch and can vary in size from thatminimum up to one inch or larger, including in gradations between theselimits. Finely divided aggregate is smaller than ⅜ inch in size andagain may be graduated in much finer sizes down to 200-sieve size or so.Fine aggregates may be present in both mortars and concretes of theinvention. The weight ratio of cement to aggregate in the dry componentsof the cement may vary, and in certain embodiments ranges from 1:10 to4:10, such as 2:10 to 5:10 and including from 55:1000 to 70:100.

The liquid phase, e.g., aqueous fluid, with which the dry component iscombined to produce the settable composition, e.g., concrete, may vary,from pure water to water that includes one or more solutes, additives,co-solvents, etc., as desired. The ratio of dry component to liquidphase that is combined in preparing the settable composition may vary,and in certain embodiments ranges from 2:10 to 7:10, such as 3:10 to6:10 and including 4:10 to 6:10.

In certain embodiments, the cements may be employed with one or moreadmixtures. Admixtures are compositions added to concrete to provide itwith desirable characteristics that are not obtainable with basicconcrete mixtures or to modify properties of the concrete to make itmore readily useable or more suitable for a particular purpose or forcost reduction. As is known in the art, an admixture is any material orcomposition, other than the hydraulic cement, aggregate and water, thatis used as a component of the concrete or mortar to enhance somecharacteristic, or lower the cost, thereof. The amount of admixture thatis employed may vary depending on the nature of the admixture. Incertain embodiments the amounts of these components range from 1 to 50%w/w, such as 2 to 10% w/w.

Admixtures of interest include finely divided mineral admixtures such ascementitious materials; pozzolans; pozzolanic and cementitiousmaterials; and nominally inert materials. Pozzolans include diatomaceousearth, opaline cherts, clays, shales, fly ash, silica fume, volcanictuffs and pumicites are some of the known pozzolans. Certain groundgranulated blast-furnace slags and high calcium fly ashes possess bothpozzolanic and cementitious properties. Nominally inert materials canalso include finely divided raw quartz, dolomites, limestone, marble,granite, and others. Fly ash is defined in ASTM C618.

Other types of admixture of interest include plasticizers, accelerators,retarders, air-entrainers, foaming agents, water reducers, corrosioninhibitors, and pigments.

As such, admixtures of interest include, but are not limited to: setaccelerators, set retarders, air-entraining agents, defoamers,alkali-reactivity reducers, bonding admixtures, dispersants, coloringadmixtures, corrosion inhibitors, dampproofing admixtures, gas formers,permeability reducers, pumping aids, shrinkage compensation admixtures,fungicidal admixtures, germicidal admixtures, insecticidal admixtures,rheology modifying agents, finely divided mineral admixtures, pozzolans,aggregates, wetting agents, strength enhancing agents, water repellents,and any other concrete or mortar admixture or additive. Admixtures arewell-known in the art and any suitable admixture of the above type orany other desired type may be used; see, e.g., U.S. Pat. No. 7,735,274,incorporated herein by reference in its entirety.

In some instances, the settable composition is produced using an amountof a bicarbonate rich product (BRP) admixture, which may be liquid orsolid form, e.g., as described in U.S. patent application Ser. No.14/112,495 published as United States Published Application PublicationNo. 2014/0234946; the disclosure of which is herein incorporated byreference.

In certain embodiments, settable compositions of the invention include acement employed with fibers, e.g., where one desires fiber-reinforcedconcrete. Fibers can be made of zirconia containing materials, steel,carbon, fiberglass, or synthetic materials, e.g., polypropylene, nylon,polyethylene, polyester, rayon, high-strength aramid, (i.e. Kevlar®), ormixtures thereof.

The components of the settable composition can be combined using anyconvenient protocol. Each material may be mixed at the time of work, orpart of or all of the materials may be mixed in advance. Alternatively,some of the materials are mixed with water with or without admixtures,such as high-range water-reducing admixtures, and then the remainingmaterials may be mixed therewith. As a mixing apparatus, anyconventional apparatus can be used. For example, Hobart mixer, slantcylinder mixer, Omni Mixer, Henschel mixer, V-type mixer, and Nautamixer can be employed.

Following the combination of the components to produce a settablecomposition (e.g., concrete), the settable compositions are in someinstances initially flowable compositions, and then set after a givenperiod of time. The setting time may vary, and in certain embodimentsranges from 30 minutes to 48 hours, such as 30 minutes to 24 hours andincluding from 1 hour to 4 hours.

The strength of the set product may also vary. In certain embodiments,the strength of the set cement may range from 5 Mpa to 70 MPa, such as10 MPa to 50 MPa and including from 20 MPa to 40 MPa. In certainembodiments, set products produced from cements of the invention areextremely durable. e.g., as determined using the test method describedat ASTM C1157.

Structures

Aspects of the invention further include structures produced from theaggregates and settable compositions of the invention. As such, furtherembodiments include manmade structures that contain the aggregates ofthe invention and methods of their manufacture. Thus in some embodimentsthe invention provides a manmade structure that includes one or moreaggregates as described herein. The manmade structure may be anystructure in which an aggregate may be used, such as a building, dam,levee, roadway or any other manmade structure that incorporates anaggregate or rock. In some embodiments, the invention provides a manmadestructure, e.g., a building, a dam, or a roadway, that includes anaggregate of the invention, where in some instances the aggregate maycontain CO₂ from a fossil fuel source, e.g., as described above. In someembodiments the invention provides a method of manufacturing astructure, comprising providing an aggregate of the invention.

Albedo Enhancing Applications

In some instances, the solid carbonate product may be employed in albedoenhancing applications. Albedo, i.e., reflection coefficient, refers tothe diffuse reflectivity or reflecting power of a surface. It is definedas the ratio of reflected radiation from the surface to incidentradiation upon it. Albedo is a dimensionless fraction, and may beexpressed as a ratio or a percentage. Albedo is measured on a scale fromzero for no reflecting power of a perfectly black surface, to 1 forperfect reflection of a white surface. While albedo depends on thefrequency of the radiation, as used herein Albedo is given withoutreference to a particular wavelength and thus refers to an averageacross the spectrum of visible light, i.e., from about 380 to about 740nm.

As the methods of these embodiments are methods of enhancing albedo of asurface, the methods in some instances result in a magnitude of increasein albedo (as compared to a suitable control, e.g., the albedo of thesame surface not subjected to methods of invention) that is 0.05 orgreater, such as 0.1 or greater, e.g., 0.2 or greater, 0.3 or greater,0.4 or greater, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.8 orgreater, 0.9 or greater, including 0.95 or greater, including up to 1.0.As such, aspects of the subject methods include increasing albedo of asurface to 0.1 or greater, such as 0.2 or greater, e.g., 0.3 or greater,0.4 or greater, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.8 orgreater, 0.9 or greater, 0.95 or greater, including 0.975 or greater andup to approximately 1.0.

Aspects of the methods include associating with a surface of interest anamount of a highly reflective microcrystalline or amorphous materialcomposition, e.g., as described above, effective to enhance the albedoof the surface by a desired amount, such as the amounts listed above.The material composition may be associated with the target surface usingany convenient protocol. As such, the material composition may beassociated with the target surface by incorporating the material intothe material of the object having the surface to be modified. Forexample, where the target surface is the surface of a building material,such as a roof tile or concrete mixture, the material composition may beincluded in the composition of the material so as to be present on thetarget surface of the object. Alternatively, the material compositionmay be positioned on at least a portion of the target surface, e.g., bycoating the target surface with the composition. Where the surface iscoated with the material composition, the thickness of the resultantcoating on the surface may vary, and in some instances may range from0.1 mm to 25 mm, such as 2 mm to 20 mm and including 5 mm to 10 mm.Applications in use as highly reflective pigments in paints and othercoatings like photovoltaic solar panels are also of interest.

The albedo of a variety of surfaces may be enhanced. Surfaces ofinterest include at least partially facing skyward surfaces of bothman-made and naturally occurring objects. Man-made surfaces of interestinclude, but are not limited to: roads, sidewalks, buildings andcomponents thereof, e.g., roofs and components thereof (roof shingles,roofing granules, etc.) and sides, runways, and other man-madestructures, e.g., walls, dams, monuments, decorative objects, etc.Naturally occurring surfaces of interest include, but are not limitedto: plant surfaces, e.g., as found in both forested and non-forestedareas, non-vegetated locations, water, e.g., lake, ocean and seasurfaces, etc.

For example, the albedo of colored granules may be readily increasedusing methods as described herein to produce a carbonate layer on thesurface of the colored roofing granules. While the thickness of thelayer of carbonate material present on the surface of the coloredroofing granules may vary, in some instances the thickness ranges from0.1 to 200 μm, such as 1 to 150 μm, including 5 to 100 μm. A variety ofdifferent types of colored granules may be coated as described above,e.g., to enhance their reflectivity without substantially diminishingtheir color, if at all. Examples of types of granules that may be coatedwith a carbonate layer as described herein include roofing granules.

Roofing granules that may be coated with a carbonate layer, e.g., toimprove their reflectivity without substantially reducing their color,if at all, may include a core formed by crushed and screened mineralmaterials, which are subsequently coated with one or more color coatinglayers comprising a binder in which is dispersed one or more coloringpigments, such as suitable metal oxides. Inorganic binders may beemployed. The binder can be a soluble alkaline silicate that issubsequently insolubilized by heat or by chemical reaction, such as byreaction between an acidic material and the alkaline silicate, resultingin an insoluble colored coating on the mineral particles. The baseparticles employed in the process of preparing the roofing granules ofthe present invention can take several forms. The base particles may beinert core particles. The core particles may be chemically inertmaterials, such as inert mineral particles, solid or hollow glass orceramic spheres, or foamed glass or ceramic particles. Suitable mineralparticles can be produced by a series of quarrying, crushing, andscreening operations, are generally intermediate between sand and gravelin size (that is, between about #8 US mesh and #70 US mesh). The coreparticles have an average particle size of from about 0.2 mm to about 3mm, e.g., from about 0.4 mm to about 2.4 mm. In particular, suitablysized particles of naturally occurring materials such as talc, slag,granite, silica sand, greenstone, andesite, porphyry, marble, syenite,rhyolite, diabase, greystone, quartz, slate, trap rock, basalt, andmarine shells can be used, as well as manufactured materials such asceramic grog and proppants, and recycled manufactured materials such ascrushed bricks, concrete, porcelain, fire clay, and the like. Solid andhollow glass spheres are available, for example, from Potters IndustriesInc., P.O. Box 840, Valley Forge, Pa. 19482-0840, such as SPHERIGLASS®solid “A” glass spheres product grade 1922 having a mean size of 0.203mm, product code 602578 having a mean size of 0.59 mm, BALLOTTINI impactbeads product grade A with a size range of 600 to 850 micrometers (U.S.Seive size 20-30), and QCEL hollow spheres, product code 300 with a meanparticle size of 0.090 mm. Glass spheres can be coated or treated with asuitable coupling agent if desired for better adhesion to the binder ofthe inner coating composition. In the granules, the particles can becoated with a coating composition that includes binder and a pigment.The coating binder can be an inorganic material, such as ametal-silicate binder, for example an alkali metal silicate, such assodium silicate.

The coatings pigments that may be used include, but are not limited toPC-9415 Yellow, PC-9416 Yellow, PC-9158 Autumn Gold, PC-9189 BrightGolden Yellow, V-9186 Iron-Free Chestnut Brown, V-780 Black, V0797 IRBlack, V-9248 Blue, PC-9250 Bright Blue, PC-5686 Turquoise, V-13810 Red,V-12600 Camouflage Green, V12560 IR Green, V-778 IR Black, and V-799Black.

Methods as described herein may also be employed to produce frac sands.Frac-sands are used in the oil and gas recovery industry to maintainporous void space in fractured geologic structure, so as to maintaingeologic fracture integrity. Methods described herein may be employed toproduce coated substrates and manufactured sands with tailorable surfacecoatings that can contribute to the buoyancy of the sand when in fluidflow. Methods as described herein may be employed to produce substratewith a closely regular patterning or irregular patterning of carbonatematerials (crystalline or amorphous) as to effectively design thesurface of the sands to maintain an above average buoyancy in the flowof fracking fluid, while the fluids are being pumped under very highpressure into the geologic fracture site. In some instances, the methodsproduce a product with a crystalline or amorphous however unreactedcementitious coating compound, such that upon contact with a secondmedium, the material could react as an expansive cement, providing voidspace for gas and fluid flow from surrounding geologic structure. Thisexpansive property could be activated by intimate fluid or gas contact,sustained fluid contact, or other magnetic or sound wave activationprovided from the geologic surface.

Methods of using the carbonate precipitate compounds described herein invarying applications as described above, including albedo enhancingapplications, as well as compositions produced thereby, are furtherdescribed in U.S. application Ser. Nos. 14/112,495 and 14/214,129; thedisclosures of which applications are herein incorporated by reference.

Ammonia Regeneration

As described above, combination of a cation source with the aqueousammonium carbonate produces a solid CO₂ sequestering carbonate and anaqueous ammonium salt. The produced aqueous ammonium salt may vary withrespect to the nature of the anion of the ammonium salt, where specificammonium salts that may be present in the aqueous ammonium salt include,but are not limited to, ammonium chloride, ammonium acetate, ammoniumsulfate, ammonium nitrate, etc.

In addition to carbonate production, e.g., as described above, aspectsof the invention may further include regenerating an aqueous captureammonia, e.g., as described above, from the aqueous ammonium salt. Byregenerating an aqueous capture ammonium is meant processing the aqueousammonium salt in a manner sufficient to generate amount of ammonium fromthe aqueous ammonium salt. The percentage of input ammonium salt that isconverted to ammonia during this regeneration step may vary, ranging insome instances from 20 to 80%, such as 35 to 55%.

Ammonia may be regenerated from an aqueous ammonium salt in thisregeneration step using any convenient regeneration protocol. In someinstances, a distillation protocol is employed. While any convenientdistillation protocol may be employed, in some embodiments the employeddistillation protocol includes heating the aqueous ammonium salt in thepresence of an alkalinity source to produce a gaseous ammonia/waterproduct, which may then be condensed to produce a liquid aqueous captureammonia.

The alkalinity source may vary, so long as it is sufficient to convertammonium in the aqueous ammonium salt to ammonia. Any convenientalkalinity source may be employed.

Alkalinity sources that may be employed in this regeneration stepinclude chemical agents. Chemical agents that may be employed asalkalinity sources include, but are not limited to, hydroxides, organicbases, super bases, oxides, and carbonates. Hydroxides include chemicalspecies that provide hydroxide anions in solution, including, forexample, sodium hydroxide (NaOH), potassium hydroxide (KOH), calciumhydroxide (Ca(OH)₂), or magnesium hydroxide (Mg(OH)₂). Organic bases arecarbon-containing molecules that are generally nitrogenous basesincluding primary amines such as methyl amine, secondary amines such asdiisopropylamine, tertiary such as diisopropylethylamine, aromaticamines such as aniline, heteroaromatics such as pyridine, imidazole, andbenzimidazole, and various forms thereof. Super bases suitable for useas proton-removing agents include sodium ethoxide, sodium amide (NaNH₂),sodium hydride (NaH), butyl lithium, lithium diisopropylamide, lithiumdiethylamide, and lithium bis(trimethylsilyl)amide. Oxides including,for example, calcium oxide (CaO), magnesium oxide (MgO), strontium oxide(SrO), beryllium oxide (BeO), and barium oxide (BaO) are also suitableproton-removing agents that may be used.

Also of interest as alkalinity sources are silica sources. The source ofsilica may be pure silica or a composition that includes silica incombination with other compounds, e.g., minerals, so long as the sourceof silica is sufficient to impart desired alkalinity. In some instances,the source of silica is a naturally occurring source of silica.Naturally occurring sources of silica include silica containing rocks,which may be in the form of sands or larger rocks. Where the source islarger rocks, in some instances the rocks have been broken down toreduce their size and increase their surface area. Of interest aresilica sources made up of components having a longest dimension rangingfrom 0.01 mm to 1 meter, such as 0.1 mm to 500 cm, including 1 mm to 100cm, e.g., 1 mm to 50 cm. The silica sources may be surface treated,where desired, to increase the surface area of the sources. A variety ofdifferent naturally occurring silica sources may be employed. Naturallyoccurring silica sources of interest include, but are not limited to,igneous rocks, which rocks include: ultramafic rocks, such as Komatiite,Picrite basalt, Kimberlite, Lamproite, Peridotite; mafic rocks, such asBasalt, Diabase (Dolerite) and Gabbro; intermediate rocks, such asAndesite and Diorite; intermediate felsic rocks, such as Dacite andGranodiorite; and Felsic rocks, such as Rhyolite, Aplite-Pegmatite andGranite. Also of interest are man-made sources of silica. Man-madesources of silica include, but are not limited to, waste streams suchas: mining wastes; fossil fuel burning ash; slag, e.g. iron slag,phosphorous slag; cement kiln waste; oil refinery/petrochemical refinerywaste, e.g. oil field and methane seam brines; coal seam wastes, e.g.gas production brines and coal seam brine; paper processing waste; watersoftening, e.g. ion exchange waste brine; silicon processing wastes;agricultural waste; metal finishing waste; high pH textile waste; andcaustic sludge. Mining wastes include any wastes from the extraction ofmetal or another precious or useful mineral from the earth. Wastes ofinterest include wastes from mining to be used to raise pH, including:red mud from the Bayer aluminum extraction process; the waste frommagnesium extraction for sea water, e.g. at Moss Landing, Calif.; andthe wastes from other mining processes involving leaching. Ash fromprocesses burning fossil fuels, such as coal fired power plants, createash that is often rich in silica. In some embodiments, ashes resultingfrom burning fossil fuels, e.g. coal fired power plants, are provided assilica sources, including fly ash, e.g., ash that exits out the smokestack, and bottom ash. Additional details regarding silica sources andtheir use are described in U.S. Provisional application Ser. No.14/112,495 filed on Oct. 17, 2013; the disclosure of which is hereinincorporated by reference.

In embodiments of the invention, ash is employed as an alkalinitysource. Of interest in certain embodiments is use of a coal ash as theash. The coal ash as employed in this invention refers to the residueproduced in power plant boilers or coal burning furnaces, for example,chain grate boilers, cyclone boilers and fluidized bed boilers, fromburning pulverized anthracite, lignite, bituminous or sub-bituminouscoal. Such coal ash includes fly ash which is the finely divided coalash carried from the furnace by exhaust or flue gases; and bottom ashwhich collects at the base of the furnace as agglomerates.

Fly ashes are generally highly heterogeneous, and include of a mixtureof glassy particles with various identifiable crystalline phases such asquartz, mullite, and various iron oxides. Fly ashes of interest includeType F and Type C fly ash. The Type F and Type C flyashes referred toabove are defined by CSA Standard A23.5 and ASTM C618. The chiefdifference between these classes is the amount of calcium, silica,alumina, and iron content in the ash. The chemical properties of the flyash are largely influenced by the chemical content of the coal burned(i.e., anthracite, bituminous, and lignite). Fly ashes of interestinclude substantial amounts of silica (silicon dioxide, SiO₂) (bothamorphous and crystalline) and lime (calcium oxide, CaO, magnesiumoxide, MgO).

The burning of harder, older anthracite and bituminous coal typicallyproduces Class F fly ash. Class F fly ash is pozzolanic in nature, andcontains less than 10% lime (CaO). Fly ash produced from the burning ofyounger lignite or subbituminous coal, in addition to having pozzolanicproperties, also has some self-cementing properties. In the presence ofwater, Class C fly ash will harden and gain strength over time. Class Cfly ash generally contains more than 20% lime (CaO). Alkali and sulfate(SO₄) contents are generally higher in Class C fly ashes.

Fly ash material solidifies while suspended in exhaust gases and iscollected using various approaches, e.g., by electrostatic precipitatorsor filter bags. Since the particles solidify while suspended in theexhaust gases, fly ash particles are generally spherical in shape andrange in size from 0.5 μm to 100 μm. Flyashes of interest include thosein which at least about 80%, by weight comprises particles of less than45 microns. Also of interest in certain embodiments of the invention isthe use of highly alkaline fluidized bed combustor (FBC) fly ash.

Also of interest in embodiments of the invention is the use of bottomash. Bottom ash is formed as agglomerates in coal combustion boilersfrom the combustion of coal. Such combustion boilers may be wet bottomboilers or dry bottom boilers. When produced in a wet or dry bottomboiler, the bottom ash is quenched in water. The quenching results inagglomerates having a size in which 90% fall within the particle sizerange of 0.1 mm to 20 mm, where the bottom ash agglomerates have a widedistribution of agglomerate size within this range. The main chemicalcomponents of a bottom ash are silica and alumina with lesser amounts ofoxides of Fe, Ca, Mg, Mn, Na and K, as well as sulphur and carbon.

Also of interest in certain embodiments is the use of volcanic ash asthe ash. Volcanic ash is made up of small tephra, i.e., bits ofpulverized rock and glass created by volcanic eruptions, less than 2millimetres in diameter.

In one embodiment of the invention, cement kiln dust (CKD) is employedas an alkalinity source. The nature of the fuel from which the ashand/or CKD were produced, and the means of combustion of said fuel, willinfluence the chemical composition of the resultant ash and/or CKD. Thusash and/or CKD may be used as a portion of the means for adjusting pH,or the sole means, and a variety of other components may be utilizedwith specific ashes and/or CKDs, based on chemical composition of theash and/or CKD.

In certain embodiments of the invention, slag is employed as analkalinity source. The slag may be used as a as the sole pH modifier orin conjunction with one or more additional pH modifiers, e.g., ashes,etc. Slag is generated from the processing of metals, and may containcalcium and magnesium oxides as well as iron, silicon and aluminumcompounds. In certain embodiments, the use of slag as a pH modifyingmaterial provides additional benefits via the introduction of reactivesilicon and alumina to the precipitated product. Slags of interestinclude, but are not limited to, blast furnace slag from iron smelting,slag from electric-arc or blast furnace processing of steel, copperslag, nickel slag and phosphorus slag.

As indicated above, ash (or slag in certain embodiments) is employed incertain embodiments as the sole way to modify the pH of the water to thedesired level. In yet other embodiments, one or more additional pHmodifying protocols is employed in conjunction with the use of ash.

Also of interest in certain embodiments is the use of other wastematerials, e.g., demolished or recycled concretes or mortars, as analkalinity source. When employed, the concrete dissolves releasing sandand aggregate which, where desired, may be recycled to the carbonateproduction portion of the process.

Of interest in certain embodiments are mineral alkalinity sources. Themineral alkalinity source that is contacted with the aqueous ammoniumsalt in such instances may vary, where mineral alkalinity sources ofinterest include, but are not limited to: silicates, carbonates, flyashes, slags, limes, cement kiln dusts, etc., e.g., as described above.In some instances, the mineral alkalinity source comprises a rock, e.g.,as described above.

While the temperature to which the aqueous ammonium salt is heated inthese embodiments may vary, in some instances the temperature rangesfrom 25 to 200, such as 25 to 185° C. The heat employed to provide thedesired temperature may be obtained from any convenient source,including steam, a waste heat source, such as flue gas waste heat, etc.

Distillation may be carried out at any pressure. Where distillation iscarried out at atmospheric pressure, the temperature at whichdistillation is carried out may vary, ranging in some instances from 50to 120, such as 60 to 100, e.g., from 70 to 90° C. In some instances,distillation is carried out at a sub-atmospheric pressure. While thepressure in such embodiments may vary, in some instances thesub-atmospheric pressure ranges from 1 to 14 psig, such as from 2 to 6psig. Where distillation is carried out at sub-atmospheric pressure, thedistillation may be carried out at a reduced temperature as compared toembodiments that are performed at atmospheric pressure.

While the temperature may vary in such instances as desired, in someembodiments where a sub-atmospheric pressure is employed, thetemperature ranges from 15 to 60, such as 25 to 50° C. Of interest insub-atmospheric pressure embodiments is the use of a waste heat forsome, if not all, of the heat employed during distillation. Waste heatsources of that may be employed in such instances include, but are notlimited to: flue gas, heat of absorption generated by CO₂ capture andresultant ammonium carbonate production; and a cooling liquid (such asfrom a co-located source of CO₂ containing gas, such as a power plant,factory etc., e.g., as described above), and combinations thereof

Aqueous capture ammonia regeneration may also be achieved using anelectrolysis mediated protocol, in which a direct electric current isintroduced into the aqueous ammonium salt to regenerate ammonia. Anyconvenient electrolysis protocol may be employed. Examples ofelectrolysis protocols that may be adapted for regeneration of ammoniafrom an aqueous ammonium salt may employed one or more elements from theelectrolysis systems described in United States Application PublicationNos. 20060185985 and 20080248350, as well as published PCT ApplicationPublication No. WO 2008/018928; the disclosures of which are herebyincorporated by reference.

The resultant regenerated aqueous capture ammonia may vary, e.g.,depending on the particular regeneration protocol that is employed. Insome instances, the regenerated aqueous capture ammonia includes ammonia(NH₃) at a concentration ranging from 4 to 20 M, such as 12.0 to 16.0 M.The pH of the aqueous capture ammonia may vary, ranging in someinstances from 10.0 to 13.0, such as 10.0 to 12.5.

In some instances, the methods further include contacting theregenerated aqueous capture ammonia with a gaseous source of CO₂, e.g.,as described above, under conditions sufficient to produce an aqueousammonium carbonate. In other words, the methods may include recyclingthe regenerated ammonia into the process. In such instances, theregenerated aqueous capture ammonia may be used as the sole captureliquid, or combined with another liquid, e.g., make up water, to producean aqueous capture ammonia suitable for use as a CO₂ capture liquid.Where the regenerated aqueous ammonia is combined with additional water,any convenient water may be employed. Waters of interest from which theaqueous capture ammonia may be produced include, but are not limited to,freshwaters, seawaters, brine waters, produced waters and waste waters.

Recycling

In some instances, the methods may include recirculating one or more ofthe reaction components from one stage of the process to another stageof the process. For example, as described above regenerated aqueousammonia may be recycled to the CO₂ capture stage. Cation salts and/oraggregates produced during ammonia regeneration may be recycled to thecarbonate production stage. Waste heat produced at one stage, e.g., CO₂capture, may be employed at another stage, e.g., ammonia regeneration,e.g., as described above. The above are non-limiting examples ofembodiments where recycling occurs.

Production of Pure CO₂ Gas

One or more stages of the methods may result in the production of CO2case. For example, during the production of solid carbonate from theaqueous ammonium carbonate, up to one mol of CO₂ may be produced forevery 2 mols of ammonium bicarbonate. Alternatively or in addition, theammonia regeneration step may result in the production of waste CO₂.While such instances may result in the production of CO₂, the overallprocess sequesters a net amount of CO₂ in a carbonate compound. Anyproduced CO₂ may be substantially pure CO₂ product gas, which may besequestered by injection into a subsurface geological location, asdescribed in greater detail below. Therefore, the process is aneffective CO₂ sequestration process. The phrase “substantially pure”means that the product gas is pure CO₂ or is a CO₂ containing gas thathas a limited amount of other, non-CO₂ components.

Following production of the CO₂ product gas in such embodiments, aspectsof the invention may include injecting the product CO₂ gas into asubsurface geological location to sequester CO₂. By injecting is meantintroducing or placing the CO₂ product gas into a subsurface geologicallocation. Subsurface geological locations may vary, and include bothsubterranean locations and deep ocean locations. Subterranean locationsof interest include a variety of different underground geologicalformations, such as fossil fuel reservoirs, e.g., oil fields, gas fieldsand un-mineable coal seams; saline reservoirs, such as saline formationsand saline-filled basalt formations; deep aquifers; porous geologicalformations such as partially or fully depleted oil or gas formations,salt caverns, sulfur caverns and sulfur domes; etc.

In some instances, the CO₂ product gas may be pressurized prior toinjection into the subsurface geological location. To accomplish suchpressurization the gaseous CO₂ can be compressed in one or more stageswith, where desired, after cooling and condensation of additional water.The modestly pressurized CO₂ can then be further dried, where desired,by conventional methods such as through the use of molecular sieves andpassed to a CO₂ condenser where the CO₂ is cooled and liquefied. The CO₂can then be efficiently pumped with minimum power to a pressurenecessary to deliver the CO₂ to a depth within the geological formationor the ocean depth at which CO₂ injection is desired. Alternatively, theCO₂ can be compressed through a series of stages and discharged as asuper critical fluid at a pressure matching that necessary for injectioninto the geological formation or deep ocean. Where desired, the CO₂ maybe transported, e.g., via pipeline, rail, truck or other suitableprotocol, from the production site to the subsurface geologicalformation.

In some instances, the CO₂ product gas is employed in an enhanced oilrecovery (EOR) protocol. Enhanced Oil Recovery (abbreviated EOR) is ageneric term for techniques for increasing the amount of crude oil thatcan be extracted from an oil field. Enhanced oil recovery is also calledimproved oil recovery or tertiary recovery. In EOR protocols, the CO₂product gas is injected into a subterranean oil deposit or reservoir.

CO₂ gas production and sequestration thereof is further described inU.S. application Ser. No. 14/861,996, the disclosure of which is hereinincorporated by reference.

Alkali Enrichment

In some instances, the methods further include subjecting the aqueousammonium carbonate to an alkali enrichment protocol, e.g., a membranemediated protocol, such as one that includes contacting first and secondliquids to opposite sides of a membrane. In such instances, the membranemay be a cationic membrane or an anionic membrane. Further detailsregarding alkali enrichment protocols, such as membrane mediated alkalienrichment protocols, are described in U.S. patent application Ser. No.14/636,043; the disclosure of which is herein incorporated by reference.In some such instances, the methods include contacting the aqueouscapture ammonia with the gaseous source of CO₂ in a combined capture andalkali enrichment reactor, where the reactor may include: a core hollowfiber membrane component, e.g., one that includes a plurality of hollowfiber membranes; an alkali enrichment membrane component surrounding thecore hollow fiber membrane component and defining a first liquid flowpath in which the core hollow fiber membrane component is present; and ahousing configured to contain the alkali enrichment membrane componentand core hollow fiber membrane component, wherein the housing isconfigured to define a second liquid flow path between the alkalienrichment membrane component and the inner surface of the housing. Insuch instances, the alkali enrichment membrane component may beconfigured as a tube and the hollow fiber membrane component is axiallypositioned in the tube. In such instances, the housing may be configuredas a tube, wherein the housing and the alkali enrichment membranecomponent are concentric.

Systems

Aspects of the invention further include systems for sequestering CO₂from a gaseous source of CO₂ via a protocol such as described above. Asystem is an apparatus that includes functional modules or reactors,e.g., as described above, that are operatively coupled in a mannersufficient to perform methods of the invention, e.g., as describedabove. Aspects of such systems include: a CO₂ gas/aqueous captureammonia module; a carbonate production module; and an aqueous captureammonia regeneration module.

In some instances, the CO₂ gas/aqueous capture ammonia module comprisesa hollow fiber membrane. In some instances, the system is operativelycoupled to a gaseous source of CO₂. As described above, the gaseoussource of CO₂ may be a multi-component gaseous stream, such as a fluegas.

Operably coupled to the CO₂ gas/aqueous capture ammonia module is acarbonate production module. Embodiments of modules include continuousreactors that are configured for producing CO₂ sequestering carbonatematerials. As the systems includes continuous reactors (i.e., flowreactors), they include reactors in which materials are carried in aflowing stream, where reactants (e.g., divalent cations, aqueousbicarbonate rich liquid, etc.) are continuously fed into the reactor andemerge as continuous stream of product. The continuous reactorcomponents of the systems are therefore not batch reactors. A givensystem may include the continuous reactors, e.g., as described herein,in combination with one or more additional elements, as described ingreater detail below.

In some embodiments, continuous reactors of the systems include: aflowing aqueous liquid, e.g., an aqueous ammonium carbonate; a divalentcation introducer configured to introduce divalent cations at anintroduction location into the flowing aqueous liquid; and a non-slurrysolid phase CO₂ sequestering carbonate material production locationwhich is located at a distance from the divalent cation introducer. Theflowing aqueous liquid is a stream of moving aqueous liquid, e.g., asdescribed above, which may be present in the continuous reactor, wherethe continuous reactor may have any convenient configuration. Continuousreactors of interest include an inlet for a liquid and an outlet for thewaste liquid, where the inlet and outlet are arranged relative to eachother to provide for continuous movement or flow of the liquid into andout of the reactor. The reactor may have any convenient structure, wherein some instances the reactor may have a length along which the liquidflows that is longer than any given cross sectional dimension of thereactor, where the inlet is at a first end of the reactor and the outletis at a second end of the reactor. The volume of the reactor may vary,ranging in some instances from 10 L to 1,000,000 L, such as 1,000 L to100,000 L.

Continuous reactors of interest further include a divalent cationintroducer configured to introduce divalent cations at an introductionlocation into the flowing aqueous liquid. Any convenient introducer maybe employed, where the introducer may be a liquid phase or solid phaseintroducer, depending on the nature of the divalent cation source. Theintroducer may be located in some instances at substantially the same,if not the same, position as the inlet for the bicarbonate rich productcontaining liquid. Alternatively, the introducer may be located at adistance downstream from the inlet. In such instances, the distancebetween the inlet and the introducer may vary, ranging in someembodiments from 1 cm to 10 m, such as 10 cm to 1 m. The introducer maybe operatively coupled to a source or reservoir of divalent cations.

Continuous reactors of interest also include a non-slurry solid phaseCO₂ sequestering carbonate material production location. This locationis a region or area of the continuous reactor where a non-slurry solidphase CO₂ sequestering carbonate material is produced as a result ofreaction of the divalent cations with bicarbonate ions of thebicarbonate rich product containing liquid. The reactor may beconfigured to produce any of the non-slurry solid phase CO₂ sequesteringcarbonate materials described above in the production location. In someinstances, the production location is located at a distance from thedivalent cation introduction location. While this distance may vary, insome instances the distance between the divalent cation introducer andthe material production location ranges from 1 cm to 10 m, such as 10 cmto 1 m.

The production location may include seed structure(s), such as describedabove. In such instances, the reactor may be configured to contact theseed structures in a submerged or non-submerged format, such asdescribed above. In non-submerged formats, the flowing liquid may bepresent on the surface of seed structures as a layer, e.g., of varyingthickness, but a gas, e.g., air, separates at least two portions of theseed structure, e.g., two different particles, such that the particlesare not submerged in the liquid.

Further details regarding such reactors that may be employed ascarbonate production modules in embodiments of the present systems areprovide in U.S. application Ser. No. 14/877,766; the disclosure of whichis herein incorporated by reference.

The aqueous capture ammonia regeneration module may vary so long is itis configured to produce ammonia from the aqueous ammonium salt, e.g.,via distillation or electrolysis, such as described above. In someinstances, the regeneration module will be configured to operate asub-atmospheric pressure, e.g., as described above, such that it willinclude one or more components for producing sub-atmospheric pressure,e.g., pumps, etc. In some instances, the regeneration module is operablycoupled to a source of generated heat, e.g., steam, and/or one or moresources of waste heat, e.g., as described above. In some embodiments,the regeneration module includes a source of alkalinity, such as amineral alkali source, e.g., as described above.

In some instances, the system is configured to recycle regeneratedaqueous capture ammonia to the CO₂ gas/aqueous capture ammonia module,e.g., as described above.

In some instances, the systems and modules thereof are industrial scalesystems, by which is meant that they are configured to processindustrial scale amounts/volumes of input compositions (e.g., gases,liquids, etc.). For example, the systems and modules thereof, e.g., CO₂contactor modules, carbonate production modules, ammonia regenerationmodules, etc., are configured to process industrial scale volumes ofliquids, e.g., 1,000 gal/day or more, such as 10,000 gal/day or more,including 25,000 gal/day or more, where in some instances, the systemsand modules thereof are configured to process 1,000,000,000 gal/day orless, such as 500,000,000 gal/day or less. Similarly, the systems andmodules thereof, e.g., CO₂ contactor modules, etc., are configured toprocess industrial scale volumes of gases, e.g., 25,000 cubic feet/houror more, such as 100,000 cubic feet/hour or more, including 250,000cubic feet/hour or more, where in some instances, the systems andmodules thereof are configured to process 500,000,000 cubic feet/hour orless, such as 100,000,000 cubic feet/hour or less.

In some embodiments, a system is in fluidic communication with a sourceof aqueous media, such as a naturally occurring or man-made source ofaqueous media, and may be co-located with a location where a CO₂sequestration protocol is conducted. The systems may be present on landor sea. For example, a system may be a land based system that is in acoastal region, e.g., close to a source of sea water, or even aninterior location, where water is piped into the system from a saltwater source, e.g., an ocean. Alternatively, a system may be a waterbased system, i.e., a system that is present on or in water. Such asystem may be present on a boat, ocean-based platform etc., as desired.In certain embodiments, a system may be co-located with an industrialplant, e.g., a power plant, at any convenient location.

FIG. 1 provides a schematic representation of a system according to anembodiment of the invention. As illustrated in FIG. 1, system 100includes a CO₂ gas/aqueous capture ammonia module 102, a carbonateproduction module 104; and an aqueous capture ammonia regenerationmodule 106. System 100 is configured so that CO₂ containing gas 108 froma source 109 (e.g., a flue gas of co-located power plant) is combinedwith aqueous ammonia capture liquid in the CO₂ gas/aqueous captureammonia module 102 so as to produce an aqueous ammonium carbonate 110which is then conveyed to the fluidically coupled carbonate productionmodule 104. In the carbonate production module 104, the aqueous ammoniumcarbonate 110 is combined with a cation source 112 under conditionssufficient to produce a solid CO₂ sequestering carbonate 114 and anaqueous ammonium salt 116. The aqueous ammonium salt 116 is thenconveyed to the fluidically coupled aqueous capture ammonia regenerationmodule 106, where it is heated, e.g., via steam from steam source 120,in the presence of a mineral alkalinity source 118. Regenerated aqueousammonia liquid 122 is then conveyed to fluidically coupled CO₂gas/aqueous capture ammonia module 102.

FIG. 2 provides a schematic representation of a system according to anembodiment of the invention, where ammonia regeneration occurs asub-atmospheric pressure and all heat is provided by waste heat sources.As illustrated in FIG. 2, system 200 includes a CO₂ gas/aqueous captureammonia module 202, a carbonate production module 204; and an aqueouscapture ammonia regeneration module 206. System 200 is configured sothat CO₂ containing gas from a source 208 (e.g., a flue of a powerplant) is combined with aqueous ammonia capture liquid in the CO₂gas/aqueous capture ammonia module 202 so as to produce an aqueousammonium carbonate 210 which is then conveyed to the fluidically coupledcarbonate production module 204. In the carbonate production module 204,the aqueous ammonium carbonate 210 is combined with a cation source 212under conditions sufficient to produce a solid CO₂ sequesteringcarbonate 214 and an aqueous ammonium salt 216. The aqueous ammoniumsalt 216 is then conveyed to the fluidically coupled aqueous captureammonia regeneration module 206, where it is heated in the presence of amineral alkalinity source 218. Waste heat cooling systems of aco-located power plant 220, flue gas 208 and CO₂ gas/aqueous captureammonia module 202 are employed as the heat sources for the regenerationmodule 206. Regenerated aqueous ammonia liquid 222 is then conveyed tofluidically coupled CO₂ gas/aqueous capture ammonia module 202.

In some instances, the CO₂ gas/aqueous capture ammonia module comprisesa combined capture and alkali enrichment reactor, the reactorcomprising: a core hollow fiber membrane component (e.g., one thatcomprises a plurality of hollow fiber membranes); an alkali enrichmentmembrane component surrounding the core hollow fiber membrane componentand defining a first liquid flow path in which the core hollow fibermembrane component is present; and a housing configured to contain thealkali enrichment membrane component and core hollow fiber membranecomponent, wherein the housing is configured to define a second liquidflow path between the alkali enrichment membrane component and the innersurface of the housing. In some instances, the alkali enrichmentmembrane component is configured as a tube and the hollow fiber membranecomponent is axially positioned in the tube. In some instances, thehousing is configured as a tube, wherein the housing and the alkalienrichment membrane component are concentric. Aspects of the inventionfurther include a combined capture and alkali enrichment reactor, e.g.,as described above.

In some instances the, the above protocols are carried out using asystem of one or more shippable modular units configured for use insequestering CO₂, e.g., as described in PCT Application Serial No.US2016/024338; the disclosure of which is herein incorporated byreference. Aspects of the units include a support, e.g., a housing orbase, having associated therewith one or more of: a CO₂ gas/liquidcontactor subunit, a carbonate production subunit, an alkali enrichmentsubunit, a water softening subunit, a cation recovery subunit, a heatexchange subunit, a reverse osmosis subunit, a nanofiltration subunit, amicrofiltration subunit, an ultrafiltration subunit, and a purified CO₂collection subunit. Modular units configured for use in the presentinvention may also include an ammonia regeneration unit, e.g., asdescribed above. Also provided are systems made up of one or more suchmodular units. Systems disclosed herein include large capacity systems,where individual modular units may contain only one type or more of agiven subunit, e.g., a CO₂ gas/liquid contactor subunit, a carbonateproduction subunit, an alkali enrichment subunit, a water softeningsubunit, a cation recovery subunit, a heat exchange subunit, a reverseosmosis subunit, a nanofiltration subunit, a microfiltration subunit, anultrafiltration subunit, and a purified CO₂ collection subunit. Aspectsof the invention include larger assemblages of multiple individualmodular units that are engaged and may have one or many individualmodular units that include a CO₂ gas/liquid contactor subunit, acarbonate production subunit, an alkali enrichment subunit, a watersoftening subunit, a cation recovery subunit, a heat exchange subunit, areverse osmosis subunit, a nanofiltration subunit, a microfiltrationsubunit, an ultrafiltration subunit, and a purified CO₂ collectionsubunit. Also provided are methods of using the units/systems in CO₂sequestration protocols.

The following examples are offered by way of illustration and not by wayof limitation.

EXPERIMENTAL

I. CO₂ Capture with Aqueous Ammonia

A. Materials & Methods:

Experiments were run in batch contacting ˜25 gal 0.5 M NH₃ (˜1 wt % NH₃)capture solution with synthetic flue gas inside of a single (quantity 1)2.5×8 Liqui-Cel membrane contactor (1.4 m2 membrane surface area). Thecapture solution was pumped through the lumenside (volume=0.15 L) of thecontactor at a flow rate of 0.5 gpm (1.9 lpm) with an applied backpressure of 25 psig. The synthetic flue gas was flowed in acounter-current flow through the shellside (volume=0.40 L) of thecontactor. The gas inlet concentrations ranged from 5-50% CO₂ (airmake-up); inlet volumes from 10-40 slpm (air+CO₂); inlet pressures from2-20 psig. During data collection the capture solution was flowedthrough the membrane contactor only once, recording CO₂ concentration(%, inlet and outlet), O₂ concentration (%, inlet and outlet), gasvolume in (slpm, air and CO₂), gas pressure (psig, inlet and outlet),liquid flow (gpm, inlet), liquid pressure (psig, inlet and outlet),liquid pH (outlet), liquid temperature (deg C., outlet), liquidconductivity (mS/cm, outlet).

The outlet liquid (post contact with synthetic flue gas) wascollected/combined in a separate tank. Experiments were repeated usingthe combined outlet liquid as the new inlet capture solution; thisallows for verification of capture solutions with different pHs.

B. Results:

The plot in FIG. 3 verifies the CO₂ absorption from synthetic flue gasas it depends on the pH of a 0.5 M NH₃ (˜1 wt % NH₃) capture solutionand the gas volume entering a single (quantity 1) 2.5×8 Liqui-Celmembrane contactor. With larger membrane contactors (greater surfacearea, longer residence time, etc.) it is expected that the percent CO₂absorption will increase significantly.

II. Mineralization

The following shows that ammonium bicarbonate solution can be used as acarbon bearing liquid in the formation of carbonate minerals whenexposed to hard water (a cation source).

A. Materials and Methods:

200 ml of ACS reagent grade ammonium bicarbonate was mixed (0.5M) with200 ml of an ACS reagent grade CaCl₂ in a dual decomposition reaction.The solutions were left to react, exposed to the atmosphere and gentlestirring with a stir plate. The solution was Buchner filtered after 5minutes and the resulting precipitate was recovered and dried at 75° C.overnight.

Resulting materials were observed by scanning electron microscope (SEM)as well as fourier transform infrared analysis (FTIR). FTIR spectra wererecorded using a Nicolet IS-10 by Thermo-Fisher with a HeNe laser and afast recovery deuterated triglycerine sulfate (DTGS) detector. Scanswere collected on a Germanium ATR crystal at resolution of 16 and atoptical velocity of 0.4747. SEM images were recorded using a HitatchiTM-3030 benchtop model.

B. Results:

The reaction resulted in a precipitate, that when separated fromsupernatant was identified both in crystal habit (FIG. 4A) as well as byFourier Transform Infrared analysis as calcite (peak identifiers 871cm⁻¹, 714 cm⁻¹). The supernatant was further identified as ammoniumchloride (peak identifiers 1100 cm⁻¹ as NH₃ and 1450 cm⁻¹ as NH₄Cl).

Further the experiment was repeated and CaCl₂ solution was titrated intothe NH₄HCO₃ solution in the presence of silica sand. The reactionyielded a distinct coating similar to coatings produced with NaHCO₃ ascarbon containing reagent.

III. Coating Process A. Materials and Methods:

0.25 M CaCl₂ was added to equal volumes of either 0.5 M NaHCO₃ or 0.5 MNa₂CO₃ in a dual decomposition reaction manner and were analyzedimmediately post mixing. The results indicate that there are twodistinct pathways toward calcium carbonate formation; a familiar onedesignated as reaction 2 (CaCl₂ (aq) and Na₂CO₃ (aq) at high pH,carbonate pathway) and another pathway designated as reaction 1 (CaCl₂(aq) into NaHCO₃ (aq) at neutral pH, bicarbonate pathway).

FTIR spectra were recorded using a Nicolet IS-10 by Thermo-Fisher with aHeNe laser and a fast recovery deuterated triglycerine sulfate (DTGS)detector. Scans were collected on a Germanium ATR crystal at resolutionof 16 and at optical velocity of 0.4747. FTIR samples were prepared byadding 0.25 M CaCl₂ (Sigma, Lot#BCBL2738 & Deionized Water) to 0.5MNaHCO₃ (Aqua Solutions, Lot #319302 & Deionized Water). 20 μl waspipetted onto the ATR crystal and the reaction was recorded in a timeresolved fashion using a Macro applied to Omnic 9.2 software. Thespectra were recorded at 0, 10, 20, and 1800 seconds.

The pH was recorded in a time resolved manner using an OrionStar A215 pHmeter with an Orion 8157BNUMD Ross Ultra pH/ATC Probe. Data was loggedusing StarCom 1.0 sampling every 3 seconds while dosing 0.25 M CaCl₂solution (Sigma, Lot#BCBL2738 & Deionized Water) into 0.5 M NaHCO₃solution (Aqua Solutions, Lot#319302 & Deionized Water) and 0.5 M Na₂CO₃(Sigma Lot#SLBD98664).

The dissolved inorganic carbon (DIC) content of solution and solidcarbonate samples were determined by acidometric titration andcoulometric detection using a CM150 carbon analysis system (UIC, Inc.).The samples were typically titrated with 2N H₂PO₄ (Sigma Aldrich). Todetect CO₂ evolved in reactions of CaCl₂ (Sigma Aldrich) with NaHCO₃(Aqua Solutions), however, the samples were not titrated with H₂PO₄, butrather, a solution of CaCl₂ was titrated with a solution of NaHCO₃because titration with H₂PO₄ would result in liberation of CO₂ fromCaCO₃. This allowed CO₂ to be quantified by coulometric detection; anysolid formed in the reaction was then isolated, dried and analyzed byFTIR to confirm its composition as CaCO₃. All analyses using the CM150system were completed at 40° C.

B. Results:

Time Resolved Fourier Transform Infrared Spectra (FTIR) of a reaction 1reaction at times of 0 seconds, 10 seconds, 30 seconds, 30 minutes postmixing shows calcite infrared active bond vibrational modes of, v3 (1400cm⁻¹), v1 (1087 cm⁻¹), v2 (877 cm⁻¹), and v4 (714 cm⁻¹). Theasymmetrical C—O stretching of the carbonate bond, v3, is seen shiftingthrough a bidentate, resulting in a characteristic calcite peaksuggesting that calcium carbonate formation may be forming through abicarbonate pathway similar to one proposed in nature. The symmetriccarbonate vibrational mode, v1, relates to free carbonate available inthe structure. Out of plane bending, v2, and in plane bending, v4, areidentified by (877 cm⁻¹) and (714 cm⁻¹) respectively. An FTIR spectraidentifying CaCO₃ (calcite) formed by LCP Reaction 1, and Reaction 2 canbe seen. The end product of both pathways appears to be identical.Nanoparticle tracking analysis (NTA) still-shot image of 0.25M NaHCO₃.Bicarbonate-rich liquid condensed phase droplets can be seen. An NTAstill-shot image of a reaction 1 immediately post mixing provides avisualization of what is measured in time-resolve fashion in part A: Thechemical pathway of LCP-driven low pH reaction (Reaction 1) vs.conventional high pH reaction (Reaction 2). The measured yields ofreaction 1 vs. reaction 2, with respect to CaCO₃ and CO₂, as determinedby DIC analysis. The results reinforce the difference between reaction 1and reaction 2 pathways due to differences in evolved CO₂ (expected forreaction 1). The time-resolved pH response of reaction 1 dump reactionshows an initial drop in pH, presumably due to removal of bicarbonate.The time-resolved pH response of reaction 2 dump reaction shows littlepH drop suggesting that carbonates are being consumed during mineralformation and are buffered by bicarbonates. During the reaction ofcarbonate formation, liquid condensed phases (LCP) evolve in thepresence of calcium ion and nucleating to form CaCO⁻³. As CaCO₃precipitation proceeds, dehydration of the reaction product occurs asseen by the drop of δ O—H vibrational peak. According to FTIR spectra,the structures were initially hydrated and amorphous as reportedpreviously, showing broad peaks in the observed range. As the reactionprogresses, however, gradual appearance of sharp peaks are related tothe development of crystalline structure of the carbonate polymorphs asseen with the increase of 1400 cm⁻¹ (v₃ asymmetrical CO₃), 1087 cm⁻¹ (v₁symmetrical CO₃), 877 cm⁻¹ (v₂ out-of-plane band of CO₃), and 714 cm⁻¹(v₄ in-plane-band of CO₃), indicating the formation of calcite phase.This particular reaction was denoted as Reaction 1 in the main reportand was compared to conventional CaCO₃ precipitation pathway, Reaction2.

CaCl₂ (aq)+2NaHCO₃ (aq)

CaCO₃(s)+2NaCl (aq)+H₂O (l)+CO₂ (g)  Reaction 1:

CaCl₂ (aq)+Na₂CO₃(aq)

CaCO₃(s)+2NaCl (aq)  Reaction 2:

The products as the result of Reaction 1 and 2 are identical. The yieldof CO₂ and CaCO₃ were 90% and 80%, respectively, confirming thestoichiometry and chemical pathway of Reaction 1. pH was also measuredin a time-resolved fashion and suggests that reaction 1 occurs at alower pH compared to the conventional Reaction 2. This is directlyrelated to LCP-formation mechanism as Ca²⁺ has the propensity tointeract with HCO₃ ⁻, enabling precipitation reaction to take place atneutral pH. In both cases, pHs in the initial stages decrease slightlydue to onset of CaCO₃ precipitation.

IV. Processing of Hard Water

Solutions that have high concentrations of divalent ions, e.g., calcium(Ca²⁺), magnesium (Mg²⁺), etc., are produced from seawater or othersaline or brine sources using existing water process technologies, e.g.,nanofiltration (NF) or reverse osmosis (RO), for use as the hard waterin the coating process as described above.

A. Materials & Methods:

Feed solutions, e.g., instant ocean (28,500 ppm TDS), calcium chloride(CaCl₂, 5,500 ppm TDS), etc., were treated with 4 in. diameter (12.57sq. in.) swatches of various commercial NF and RO membrane elements. Themembrane permeate flux (gallons per square foot per day, GFD) wasregulated by a valve at the concentrate stream of the flat-plate testingsystem. Samples of permeate were analyzed by ion chromatography and/orconductivity probe to determine the percent ion rejection of a givenmembrane. System pressure (psig) was also recorded during screening.

B. Results:

With simulated seawater as the feed solution, we were able to verify toa good degree the passage of monovalent ions and the rejection ofdivalent ions using commercial NF membranes. With CaCl₂ solution, weverified that there are commercial NF membranes (e.g., TS40 (TriSep) andESNA1-LF2 (Hydranautics)) capable of achieving greater than 80%calcium-ion rejection.

V Ammonia Reformation with Geomass

A. Ammonia Reformation

Different types of geomass, e.g., high surface area carbonate orsilicate solids, waste materials like fly ash, slag, bottom ash,economizer ash, red mud, etc., are heated in the presence of theback-end process water containing ammonium salt to regenerate ammoniagas (NH₃) from ammonium salts (NH₄ ⁺). It takes place in a recoverytower akin to that used in the industrially developed Solvay process.

The ammonia reformation regenerates the reactive capture solution forcontact with the flue gas, ultimately absorbing and converting gaseousCO₂ into bicarbonate ion (HCO₃ ⁻) in aqueous solution. Ammonia (NH₃) isconverted to ammonium (NH₄ ⁺) in the CO₂ capture process, while NH₄ ⁺ isconverted back to NH₃ in the ammonia reformation process. In otherwords, NH₃ is not consumed in any part of the process. It merelyfacilitates the sequestration of gaseous CO₂ into aqueous HCO₃ ⁻ whichthen mineralizes into carbonate (CO₃ ²⁻) in the coating process.

Ammonia (NH₃) is regenerated by heating aqueous ammonium salts, e.g.,ammonium chloride (NH₄Cl), ammonium acetate (NH₄OAc), etc., in thepresence of geomass fines, e.g., limestone, fly ash, slag, basalt, etc.,for reuse in CO₂ absorption process at the front-end of the carboncapture and mineralization protocol, e.g., as illustrated in FIG. 1.

1. Materials & Methods

5-20 mL of ammonium salt solutions (0.5 M—saturated) were added tosample vessels containing geomass fines (2-10 g) and the vessel washeated to 30-150° C. for 15-126 min. A low flow of air (pre-scrubbed w/8M KOH solution) was passed through the suspension during heating. Anyvolatile ammonia gas (NH₃) was trapped as ammonium (NH⁴⁺) in an acidscrubber (5 mL 1 M HCl). The NH⁴⁺ in the acid scrubber was thenquantified by ion chromatography; ‘NH₃ Reformation Yield (%)’ in thefigures below represents the measured quantity of NH⁴⁺ from ionchromatography divided by the theoretical yield of NH₃ (based on volumeand concentration of ammonium salt added to the geomass fines).

2. Results

The regeneration of ammonia (NH₃) from ammonium salts was verified in anumber of systems that varied the geomass fines, ammonium salts andtheir concentrations, reaction temperature and reaction time. Ammoniareformation yields in excess of 40% were observed at temperatures as lowas 75° C. after heating for only 30 minutes, as further illustrated inFIG. 4.

As shown in FIG. 4, ammonia (NH₃) reformation occurs by heatingdifferent types of geomass, e.g., fly ash, CaCO₃, basalt, etc., in thepresence of an ammonium (NH⁴⁺) salt solution, e.g., ammonium chloride(NH₄Cl), ammonium acetate (NH₄OAc), ammonium nitrate (NH₄NO₃), etc. Thebar chart (left vertical axis) shows the experimental yield of NH₃reformation, while the line chart (right vertical axis) shows theconcentration of NH₃ recovered in the reformed solution. What these twodata sets show is that while the NH₃ reformation yield may be low, e.g.,10% for CaCO₃ geomass, the concentration of NH₃ recovered in that samesystem can be quite high, e.g., 415 mM, creating an effective CO₂capture solution for removal of CO₂ from a flue gas.

As shown in FIG. 5, NH₃ reformation yield in the absence of any geomassis comparatively much lower. The exception being ammonium bicarbonate(NH₄HCO₃), which does yield 30% NH₃ in the presence of heat, howeverunwanted CO₂ is also evolved from this system. In essence, this chartillustrates the benefits of geomass in driving the NH₃ reformationprocess. FIG. 6 provides data verifying NH₃ reformation from NH₄Cl at75° C. and in the presence of different types of geomass. The resultsdemonstrate that the NH₃ reformation can occur at low temperatures inthe presence of common types of geomass, e.g., fly ash, CaCO₃ andbasalt.

B. Additional Studies with Different Types of Geomass1. Studies were performed to assess the ability of recycledconcrete/mortar to act as an alkalinity geomass source for ammoniareformation. FIG. 7 shows plots of “Geomass Alkalinity (mmol) vs Time(min)” for different basalt and recycled concrete/mortar geomassmaterials; 1 M HCl was titrated into a suspension of 0.25 g geomass insaturated ammonium chloride solution at 70 degrees C. until a pH of 3.30was maintained. The data represent the rate of release of alkalinityfrom geomass upon exposure to fresh ammonium chloride solution.2. Studies were performed to assess the ability of recycledconcrete/mortar, among other materials, to act as an alkalinity geomasssource for ammonia reformation. The bar chart in FIG. 8 shows the “IonConcentration in Reformed Liquid (mmol/L)” for sodium (Na+), potassium(K+), calcium (Ca2+) and magnesium (Mg2+), that were leached fromdifferent geomass materials upon mixing with 2 M ammonium chloridesolution for 10 minutes at room temperature; CKD=cement kiln dust,CCR=coal combustion residue. Remaining solids were separated byfiltration and the filtrates or “reformed liquids” were analyzed by ionchromatography. The data demonstrate the ability of various materials toact as a source of Ca²⁺ for making a solid carbonate materials.C. Ammonia Reformation with Vacuum Distillation

Studies were performed to assess the impact of sub-atmospheric pressureon ammonia reformation. The chart in FIG. 9 shows the concentration(mol/L) of calcium and of alkalinity in the reformer liquid, as wasdetermined by ion chromatography and acid titration, respectively, afterit was reformed in the presence of electric arc furnace steel slag.Higher calcium ion concentration and lower alkalinity is observed in thereformer liquid for trials with vacuum compared to trials with no vacuum(labeled as “55 C, No Vacuum”). The control trials, “55 C, No Slag” and“55 C, Water” showed minimal reaction.

VI. Various Representative Systems A. A 2 MW Coal Fired Power Plant

FIG. 7 provides an illustration of a system according to an embodimentof the invention that is suitable for use with a 2 MW coal fired powerplant. The specific parameters outlined in the process diagram are basedon the rate of CO₂ capture. At 50% capture, that equates to roughly2,250 lb CO₂ per hour or about 390 moles of CO₂ per minute. For example,the US EPA reports that the average CO2 emissions from coal-fired powerstations in the US is 2,249 lb CO₂ per MW per hour (see the websitehaving an address in which “www.” is positioned before“epa.gov/energy”). Assuming 24-7 operation and 50% CO₂ capture, then:

${\frac{2,250\mspace{14mu} {lb}\mspace{14mu} {CO}\; 2}{{MW}\mspace{14mu} h} \times 2\mspace{14mu} {MW} \times 50\%} = \frac{2,250\mspace{14mu} {lb}\mspace{14mu} {CO}\; 2}{h}$

In other words, the parameters for the streams in the diagram, e.g.,temperature, concentration, volume, flow, etc., correspond to processingroughly 2,250 lb CO₂ per hour with the 2 MW demonstration power plant.

The associated chemical pathways implemented in the system illustratedin FIG. 10 are:

CO₂+NH₃+H₂O=>NH₄HCO₃  Step 1:

2NH₄HCO₃+CaCl₂=>CaCO₃+2NH₄Cl+H₂CO₃  Step 2:

NH₄Cl+Geomass(Earthen Alkaline Minerals, i.e. CaO, CaOH₂, CaCO₃, MgO,MgOH₂, etc.)=>NH₃+Hard Water  Step 3:

B. Additional 2 MW Coal Fired Power Plant Systems

FIGS. 11A, 11B and 11C provide system diagrams for three different 2 MWcoal fired power plants.

Generally:

-   -   Process changes revolve around the geomass reformer and its        output to the front-end CO₂ capture block.    -   Temperatures indicated in certain instances.    -   Open system w/storage tanks to run in semi-continuous mode        w/option to recycle, also minimizing cooling loads.    -   Higher concentrations of reagents throughout, minimize heating        load in the reformer.

Specifically:

-   -   FIG. 11A increases the concentration of NH₃ coming from the        reformer, which in turn reduces volume of water vapor and likely        the energy needed for heating    -   FIG. 11B reintroduces the secondary contactor block for        absorbing NH₃ gas coming from the reformer    -   FIG. 11C proposes pre-mixing the NH₃ gas from the reformer w/the        flue gas from the slip-stream prior to entering the contactors        for CO₂ absorption

C. A 10 MW Coal Fired Power Plant

FIG. 12 provides an illustration of a system according to an embodimentof the invention that is suitable for use with a 10 MW coal fired powerplant. The estimated mass flow balance for a process which is removing50% of the carbon dioxide from a 10 MW slip-stream of coal-fired powerplant flue gas is shown. A total of 14,643 kg/hr of low grade steam and3176 gal/min of cooling water is employed. The cooling water has a deltadifference of 10° C. between entrance and exit temperatures. The fluegas is assumed to be 12% wt carbon dioxide and enter at approx. 105° F.

D. A 10 MW Coal Fired Power Plant With a Reduce Pressure AmmoniaReformer

FIG. 13 provides the integrated mass flow diagram for a systemincorporating three proposed parasitic-load, cooling water-reducingtechniques. As illustrated in FIG. 13, by running the reformercontinuously at a vacuum, therefore lowering its operating temperature(approx. 70° F. in this example) and increasing the electric pump loadon the reformer, the heat of the flue gas (H1), the heat of absorption(H2), and the heat of the recirculation water for the coal plant in thisexample (H3) may be employed. This is due to the lower temperature thatthe reformer is able to use by increasing the vacuum under which thereformation occurs. This configuration significantly reduces/eliminatesthe steam requirement (to zero in this case with respect to FIG. 12) andthe cooling water requirement (approx. 33% reduction in this case withrespect to FIG. 12). Additionally, the recirculation water at thiscoal-fired power plant may be cooled to a temperature approaching thereformer temperature. This simultaneously supplies the process withneeded heat to reform, reduces steam requirements, and cools therecirculation water for further use by the mother coal-fired plant.

Notwithstanding the appended clauses, the disclosure is also defined bythe following clauses:

1. A method of sequestering CO₂ from a gaseous source of CO₂, the methodcomprising:

a) contacting an aqueous capture ammonia with a gaseous source of CO₂under conditions sufficient to produce an aqueous ammonium carbonate;

b) combining a cation source and the aqueous ammonium carbonate underconditions sufficient to produce a CO₂ sequestering carbonate and anaqueous ammonium salt; and

c) regenerating aqueous capture ammonia from the aqueous ammonium salt;

to sequester CO₂ from the gaseous source of CO₂.

2. The method according to Clause 1, wherein the aqueous capture ammoniacomprises ammonia at a concentration ranging from 4.0 to 20.0 M.3. The method according to any of the preceding clauses, wherein thegaseous source of CO₂ is a multi-component gaseous stream.4. The method according to Clause 3, wherein the gaseous source of CO₂is a flue gas.5. The method according to Clause 4, wherein the flue gas is obtainedfrom an industrial source.6. The method according to any of the preceding clauses, wherein thegaseous source of CO₂ is contacted with the aqueous capture ammoniausing membrane contactor.7. The method according to Clause 6, wherein the membrane contactor is ahollow fiber membrane contactor.8. The method according to any of the preceding clauses, wherein theaqueous ammonium carbonate comprises at least one of ammonium carbonateand ammonium bicarbonate.9. The method according to any of the preceding clauses, wherein theaqueous ammonium carbonate comprises both ammonium carbonate andammonium bicarbonate.10. The method according to any of the preceding clauses, whereinregenerating the aqueous capture ammonia from the aqueous ammonium saltcomprises distillation.11. The method according to Clause 10, wherein the distillation isperformed at a sub-atmospheric pressure.12. The method according to Clause 11, wherein the sub-atmosphericpressure ranges from 1 to 14 psig.13. The method according to any of Clauses 10 to 12, wherein thedistillation comprises heating the aqueous ammonium salt in the presenceof a mineral alkalinity source.14. The method according to Clause 13, wherein the mineral alkalinitysource comprises a silicate, a carbonate, fly ash, slag, lime or cementkiln dust.15. The method according to Clause 13, wherein the mineral alkalinitysource comprises a rock.16. The method according to any of Clauses 10 to 15, wherein thedistillation employs a waste heat.17. The method according to Clause 16, wherein the waste heat isprovided from a source selected from the group consisting of flue gas,heat of absorption generated by step (a) and a cooling liquid, andcombinations thereof.18. The method according to any of Clauses 1 to 9, wherein regeneratingthe aqueous capture ammonia from the aqueous ammonium salt compriseselectrolysis.19. The method according to any of the preceding clauses, wherein themethod further comprises contacting the regenerated aqueous captureammonia with a gaseous source of CO₂ under conditions sufficient toproduce an aqueous ammonium carbonate.20. The method according to any of the preceding clauses, wherein thecation source comprises an alkaline earth metal cation.21. The method according to Clause 20, wherein the cation source is asource of divalent cations.22. The method according to Clause 21, wherein the divalent cationscomprise alkaline earth metal cations.23. The method according to Clause 22, wherein the divalent alkalineearth metal cations are selected from the group consisting of Ca²⁺ andMg²⁺, and combinations thereof.24. The method according to any of Clauses 20 to 23, wherein thecombining step (b) comprises introducing the cation source into aflowing aqueous ammonium carbonate under conditions sufficient such thata non-slurry solid CO₂ sequestering carbonate is produced in the flowingaqueous ammonium carbonate.25. The method according to Clause 24, wherein the solid CO₂sequestering carbonate is a particulate composition.26. The method according to Clause 24, wherein the method comprisesproducing the solid CO₂ sequestering carbonate in association with aseed structure.27. The method according to Clause 26, wherein the solid CO₂sequestering carbonate is produced on at least one of a surface of or ina depression of the seed structure.28. The method according to any of the preceding clauses, wherein themethod further comprises producing a building material from the solidCO₂ sequestering carbonate material.29. The method according to Clause 28, wherein the building materialcomprises an aggregate.30. The method according to Clause 29, where the seed structure is aporous, permeable aggregate material that is in-filled by the solid CO₂sequestering carbonate to produce a less porous, denser solid aggregateas compared to the seed structure.31. The method according to Clause 30, where the in-filled aggregate isin-filled on the outer margin to a larger extent than in the innerportion, making the new aggregate less dense in the inner region ascompared to the outer margin, to produce a light weight aggregate.32. The method according to Clause 28, wherein the building materialcomprises roofing granules.33. A system for sequestering CO₂ from a gaseous source of CO₂, thesystem comprising:

a CO₂ gas/aqueous capture ammonia module;

a carbonate production module; and

an aqueous capture ammonia regeneration module.

34. The system according to Clause 33, wherein the CO₂ gas/aqueouscapture ammonia module comprises a hollow fiber membrane.35. The system according to Clause 33 or 34, wherein the system isoperatively coupled to a gaseous source of CO₂.36. The system according to any of Clauses 33 to 35, wherein the gaseoussource of CO₂ is a multi-component gaseous stream.37. The system according to Clause 36, wherein the gaseous source of CO₂is a flue gas.38. The system according to any of Clauses 33 to 37, wherein the aqueouscapture ammonia regeneration module comprises is configured to produceaqueous capture ammonia by distillation.39. The system according to Clause 38, wherein the aqueous captureammonia regeneration module is configured to produce aqueous captureammonia by distillation at sub-atmospheric pressure.40. The system according to Clauses 38 and 39, wherein the aqueouscapture ammonia regeneration module is operably coupled to a waste heatsource.41. The system according to any of Clauses 38 to 40, wherein the aqueouscapture ammonia regeneration module comprises a mineral alkali source.42. The system according to any of Clauses 33 to 37, wherein the aqueouscapture ammonia regeneration module is configured to produce aqueouscapture ammonia via electrolysis.43. The system according to any of Clauses 33 to 42, wherein the systemis configured to recycle regenerated aqueous capture ammonia to the CO₂gas/aqueous capture ammonia module.

Although the foregoing invention has been described in some detail byway of illustration and example for purposes of clarity ofunderstanding, it is readily apparent to those of ordinary skill in theart in light of the teachings of this invention that certain changes andmodifications may be made thereto without departing from the spirit orscope of the appended claims.

Accordingly, the preceding merely illustrates the principles of theinvention. It will be appreciated that those skilled in the art will beable to devise various arrangements which, although not explicitlydescribed or shown herein, embody the principles of the invention andare included within its spirit and scope. Furthermore, all examples andconditional language recited herein are principally intended to aid thereader in understanding the principles of the invention and the conceptscontributed by the inventors to furthering the art, and are to beconstrued as being without limitation to such specifically recitedexamples and conditions. Moreover, all statements herein recitingprinciples, aspects, and embodiments of the invention as well asspecific examples thereof, are intended to encompass both structural andfunctional equivalents thereof.

Additionally, it is intended that such equivalents include bothcurrently known equivalents and equivalents developed in the future,i.e., any elements developed that perform the same function, regardlessof structure. The scope of the present invention, therefore, is notintended to be limited to the exemplary embodiments shown and describedherein. Rather, the scope and spirit of present invention is embodied bythe appended claims.

1. A method of sequestering CO₂ from a gaseous source of CO₂, the methodcomprising: a) contacting an aqueous capture ammonia with a gaseoussource of CO₂ under conditions sufficient to produce an aqueous ammoniumcarbonate; b) combining a cation source and the aqueous ammoniumcarbonate under conditions sufficient to produce a CO₂ sequesteringcarbonate and an aqueous ammonium salt; and c) regenerating aqueouscapture ammonia from the aqueous ammonium salt; to sequester CO₂ fromthe gaseous source of CO₂.
 2. The method according to claim 1, whereinthe aqueous capture ammonia comprises ammonia at a concentration rangingfrom 4.0 to 20.0 M.
 3. The method according to claim 1, wherein thegaseous source of CO₂ is a multi-component gaseous stream.
 4. The methodaccording to claim 3, wherein the gaseous source of CO₂ is a flue gas.5. The method according to claim 4, wherein the flue gas is obtainedfrom an industrial source.
 6. The method according to claim 1, whereinthe gaseous source of CO₂ is contacted with the aqueous capture ammoniausing membrane contactor.
 7. The method according to claim 6, whereinthe membrane contactor is a hollow fiber membrane contactor.
 8. Themethod according to claim 1, wherein the aqueous ammonium carbonatecomprises at least one of ammonium carbonate and ammonium bicarbonate.9. The method according to claim 1, wherein the aqueous ammoniumcarbonate comprises both ammonium carbonate and ammonium bicarbonate.10. The method according to claim 1, wherein regenerating the aqueouscapture ammonia from the aqueous ammonium salt comprises distillation.11. The method according to claim 10, wherein the distillation isperformed at a sub-atmospheric pressure.
 12. The method according toclaim 11, wherein the sub-atmospheric pressure ranges from 1 to 14 psig.13. The method according to claim 10, wherein the distillation comprisesheating the aqueous ammonium salt in the presence of a mineralalkalinity source.
 14. The method according to claim 13, wherein themineral alkalinity source comprises a silicate, a carbonate, fly ash,slag, lime or cement kiln dust.
 15. The method according to claim 13,wherein the mineral alkalinity source comprises a rock.
 16. The methodaccording to claim 10, wherein the distillation employs a waste heat.17. The method according to claim 16, wherein the waste heat is providedfrom a source selected from the group consisting of flue gas, heat ofabsorption generated by step (a) and a cooling liquid, and combinationsthereof.
 18. (canceled)
 19. The method according to claim 1, wherein themethod further comprises contacting the regenerated aqueous captureammonia with a gaseous source of CO₂ under conditions sufficient toproduce an aqueous ammonium carbonate. 20-23. (canceled)
 24. The methodaccording to claim 1, wherein the combining step (b) comprisesintroducing the cation source into a flowing aqueous aqueous ammoniumcarbonate under conditions sufficient such that a non-slurry solid CO₂sequestering carbonate is produced in the flowing aqueous ammoniumcarbonate. 25-32. (canceled)
 33. A system for sequestering CO₂ from agaseous source of CO₂, the system comprising: a CO₂ gas/aqueous captureammonia module; a carbonate production module; and an aqueous captureammonia regeneration module. 34-43. (canceled)